The board of directors _____ yet to reach a final decision on the merger.

• A. have
• B. has (Answer)
• C. having
• D. had

'Board of directors' functions as a singular collective noun here, acting as one unit that collectively 'has' not yet decided. 'Have' would incorrectly treat the board as multiple separate deciding entities. 'Having' is a participle, grammatically incompatible with the need for a finite verb, and 'had' would shift to past perfect, inconsistent with the present relevance implied by 'yet'.

_____ the CEO nor the board members were willing to comment on the allegations.

• A. Either
• B. Neither (Answer)
• C. Not
• D. No

'Neither...nor' pairs correctly with the sentence's negative structure, negating both the CEO's and the board members' willingness to comment. With 'neither...nor', the verb agrees with the nearer subject ('board members', plural), matching 'were'. 'Either' requires 'or', not 'nor', and 'not'/'no' do not form standard correlative pairs with 'nor'.

It is imperative that the committee _____ its findings before the parliamentary session begins.

• A. publishes
• B. publish (Answer)
• C. published
• D. will publish

'It is imperative that' is a fixed subjunctive trigger, requiring the bare form of the verb regardless of subject: 'that the committee publish', not 'publishes'. This mandative subjunctive pattern is tested at the advanced level because the singular 'committee' tempts the standard indicative '-es' ending, which is incorrect here.

So thorough _____ the investigation that no loophole remained unexamined.

• A. was (Answer)
• B. is
• C. were
• D. had been

Fronting 'So thorough' at the start of a sentence triggers subject-auxiliary inversion: 'So thorough was the investigation'. Since the investigation is a single past event, the simple past 'was' is required, matching the past-tense subordinate clause. 'Is' is inconsistent tense-wise, 'were' does not agree with the singular subject, and 'had been' would wrongly imply completion before another past event.

Rarely _____ such unanimous support for a controversial policy in recent political history.

• A. has there been (Answer)
• B. there has been
• C. there have been
• D. have there been

The negative adverb 'Rarely' at the start of a sentence requires subject-auxiliary inversion: 'has there been', not the normal word order 'there has been'. Since 'support' is singular/uncountable, the singular auxiliary 'has' is required, not 'have'. This combines inversion after a fronted negative adverb with correct verb agreement.

Not until the final report _____ submitted did the true scale of the fraud become apparent.

• A. was
• B. is
• C. has been
• D. had been (Answer)

'Not until X had been submitted did Y become apparent' uses the past perfect in the 'until' clause to show the submission occurred before the realisation. Since the main clause is already in simple past with inversion ('did...become apparent'), the earlier event requires past perfect 'had been', following standard sequence-of-tenses logic for a two-stage past narrative.

The evidence, _____ scrutinised by three independent experts, was ultimately ruled inadmissible.

• A. having been thoroughly (Answer)
• B. having thoroughly
• C. thoroughly having
• D. thorough having been

The absolute/participial construction requires the passive perfect participle 'having been thoroughly scrutinised', since 'the evidence' cannot perform the action of scrutinising — it must receive the action. 'Having thoroughly' incorrectly implies the evidence itself examined something, and the remaining options scramble the word order into ungrammatical sequences.

The two witnesses' accounts, though broadly consistent, _____ found to differ on the exact timeline.

• A. was
• B. is
• C. were (Answer)
• D. has been

The true subject is 'the two witnesses' accounts' (plural). The intervening concessive clause 'though broadly consistent' distances the verb from its true subject and tempts a singular verb, but 'were' is required to agree with the plural subject 'accounts'. This long-distance agreement trap within a concessive clause is a hallmark of the most advanced exam questions.

Seldom _____ a verdict so thoroughly divided public opinion in recent memory.

• A. a verdict has
• B. has a verdict (Answer)
• C. a verdict have
• D. have a verdict

The negative adverb 'Seldom' at the start of the sentence requires subject-auxiliary inversion: 'has a verdict' (auxiliary before subject), not normal word order. Since 'a verdict' is singular, the auxiliary must also be singular: 'has', not 'have'. This isolates the inversion word order itself, requiring both correct inversion and correct number agreement.

Only after the second independent audit _____ confirmed the discrepancies was the chief financial officer asked to resign.

• A. having
• B. had (Answer)
• C. has
• D. have

The fronted restrictive adverbial 'Only after X' requires the subordinate clause to express an action completed before the main clause's past event ('was...asked to resign'). The past perfect 'had confirmed' shows the audit's confirmation preceded the resignation request. 'Having' would create an incomplete participial fragment, and 'has'/'have' are present perfect forms, inconsistent with the past-tense narrative and sequence-of-tenses requirement.