Parallelism

The gap. One verb governs the whole list — requires applicants to… — and the first two elements commit it to infinitives: to relocate, to teach. The third slot has to continue that series. The trap is that every option is grammatical on its own; the test is not "is this correct English" but "does this match the machinery the sentence already built."

The answers.

(A) switches to a that-clause. Readable alone — but requires X to relocate, to teach, and that they publish makes one verb govern two different constructions mid-sentence. The original’s drift, left in place.

(B) offers the other form that feels parallel-ish: a gerund. After two to-phrases, publishing breaks the series exactly where lists usually break — the last element.

(C) — correct. The third infinitive. Read it back through the governing verb: requires applicants to relocate…, to teach…, and to publish… — one frame, three matching complements, nothing left over.

(D) restarts the sentence inside the list: they must publish is an independent clause, and the list cannot absorb one.

(E) is a noun phrase — idiomatic by itself, which is its bait, and formless against two infinitives.

The gap. The engine is three things, and the first two fix the shape: quieter, more economical to run — comparative adjective phrases. The third slot must be a third one. The tell sits in the first two elements: once you have seen two comparatives, you know the shape of the answer before reading a single option — which converts this item from judging five candidates to matching one template.

The answers.

(A) breaks off into an independent clause — it requires less maintenance — the classic last-element drift the stem reproduces.

(B) swaps in a participle, requiring less maintenance. It hangs grammatically, but the series was adjectives, not -ing phrases.

(C) restarts with a new subject — its maintenance requirements are lower — a full clause where the list wants a quality.

(D) — correct. Less demanding to maintain mirrors more economical to run piece for piece: comparative, adjective, to-infinitive tail. Read back: quieter, more economical to run, and less demanding to maintain — three qualities, one rhythm.

(E) is a prepositional phrase — with lower maintenance requirements — attached, not parallel.

The gap. Not only … but also is a correlative pair, and correlatives photocopy structure: whatever form follows not only is the form that must follow but also. Here not only is followed by to investigate — an infinitive — so the second half is already decided before the options are read. The wrong answers are five ways of ignoring the photocopy.

The answers.

(A) follows but also with for recommending — preposition plus gerund against a bare infinitive. The mismatch the stem ships with.

(B) — correct. Not only to investigate … but also to recommend. The pair carries the same form on both sides; the sentence closes cleanly with the building code as the object.

(C) inserts a clause — it was also to recommend — restarting the sentence inside the correlative.

(D) drops to a bare participle, also recommending: the gerund trap in correlative clothing.

(E) goes subjunctive — also that it recommend — a clause where the first half placed an infinitive.

The gap. Whether X or Y — and X is doing less work than it appears: the sentence says because of drought, so the shared scaffold is because of, and X itself is just the bare noun drought. Y needs to supply only what X supplied: a bare noun. The trap is psychological as much as grammatical — the structurally right answer is the shortest on the list, and test-takers distrust short answers precisely when the exam is rewarding them.

The answers.

(A) builds a cleft clause — it was flooding that caused it — a whole sentence where the first branch placed one word.

(B) writes because flooding caused it: a clause with because, not a noun under the already-present because of. The scaffold gets duplicated and mismatched at once.

(C) — correct. Flooding. Read the frame through: abandoned because of drought or flooding — one preposition, two nouns, the comparison the sentence was built to make. Nothing else is needed, so anything else is excess.

(D) repeats the scaffold inside the second branch — it was because of flooding — a clause again, and redundant with the because of already standing.

(E) re-imports whether into its own branch — whether flooding caused it — nesting the question inside itself.

The gap. The survey asked residents three things, and the first two are indirect questions: how often they used…, what improvements they would prioritise. The third slot must be a third indirect question. The distractors work because every one of them is a thing a survey could plausibly ask about — the ear accepts them as content; only the form test separates them.

The answers.

(A) is a noun phrase — their willingness to pay — reportable content, but not a question. The last-element drift, verbatim from the stem.

(B) — correct. Whether they would be willing to pay a higher fare — the third indirect question, matching how and what with whether. Read the series back through asked: three questions, one verb, no seams.

(C) patches the noun phrase with a preposition — about their willingness — which makes it attachable, not parallel.

(D) uses direct-question word order — would they be willing — inside an indirect construction; the inversion belongs in quotation marks the sentence does not have.

(E) contorts toward a clause — if their willingness … existed — a shape no survey question takes; it exists to be eliminated and to make (A) look cleaner.

The gap. The recovery demands three things, and the first two are plural, unquantified noun phrases: specialised vessels, months of planning. The third element must join that series — and this item plants two options close enough that "noun phrase" alone will not separate them. The list’s own pattern does: plural, no article, adjective plus noun.

The answers.

(A) trails a relative clause — budgets that are considerable — inflating the noun phrase the series wants into a small sentence.

(B) is the sly one: that budgets be considerable is a legitimate complement of demands on its own — the subjunctive after a demand-verb. But the sentence already chose its construction: two noun objects. A that-clause spliced onto them makes one verb run two machineries at once.

(C) — correct. Considerable budgets — plural, bare, adjective plus noun, the exact silhouette of specialised vessels and months of planning. Read back: three demands, one shape.

(D) converts to a gerund phrase — budgeting considerably — an activity where the list names resources.

(E) is the near-miss the item was built around: a considerable budget is the right family — a clean noun phrase — with the wrong number and an article the series never uses. Against two plural, unquantified elements, the singular breaks the pattern the list itself established; this is where matching the form-family without matching the pattern costs the point.

The gap. The comparison scaffold is differ less in X than in Y, and X is already on the table: the accuracy of their results — in plus a noun-of-noun phrase. The scaffold demands the same kind of object under the second in. The difficulty is that the most fluent-sounding option is not the most parallel one: this is the item where everyday speech and exam structure part ways, and the options are engineered to make the ear vote against the frame.

The answers.

(A) is how a fluent speaker would say it — in how long they take to complete — and that is its trap: it keeps the preposition but hangs an indirect-question clause under it, where the first branch hung a noun phrase. Among these five, the sentence that photocopies its own first half exists, so the merely idiomatic one loses.

(B) drops the in that than requires here: less in X than how long… leaves the second branch dangling outside the comparison’s frame.

(C) — correct. In the length of time they require — in plus noun-of-noun, the structural twin of in the accuracy of their results. Read the whole comparison back: differ less in the accuracy of their results than in the length of time they require — two branches, one construction.

(D) substitutes a participle — in taking longer to complete — and quietly smuggles a verdict (longer) into what the sentence frames as a neutral dimension of difference.

(E) loses the preposition entirely and garbles the possessive — their length of time to complete — a phrase with no frame to sit in.

The gap. The critics argue that three things — and the first two arrive fully equipped: that it would raise costs…, that it would concentrate…. The that is not decoration; it is the reporting machinery that keeps each claim inside argue. The third claim must carry its own. What makes the item hard is that the mistake is an omission — nothing looks wrong in the bare version until you ask who is asserting the third claim.

The answers.

(A) drops the that — and with it, the third claim floats free of argue. Its environmental benefits are unproven reads as the sentence’s own assertion spliced onto the critics’ two, not as the critics’ third point. One missing word changes who is speaking; that is the whole item.

(B) — correct. That its environmental benefits are unproven — the third governed clause. Read the series back through argue: three claims, all reported, all the critics’.

(C) collapses to a with-phrase — with unproven environmental benefits — descriptive baggage where the list reports claims.

(D) hangs a participle — having unproven environmental benefits — off nothing the sentence provides.

(E) keeps the that and is still wrong, which is why it earns its place: it converts the claim into an existence statement — that unproven environmental benefits exist — asserting there are benefits (unproven ones), where the critics assert the benefits are unproven. Same words, reversed claim; the grammar survives and the meaning does not.