The sentence below is split into four segments. Identify the segment that contains a grammatical error, if any. If the sentence is free of errors, select 'No error' as your choice.

The director insisted of staff (A) / to complete the audit even (B) / though several employees weren’t ready (C) / to begin the work (D) .

The correct option is A.

Explanation:
Segment (A) contains a grammatical error in the choice of preposition following the verb "insist".

The verb "insist" does not take the preposition "of". Instead, it should be followed by the preposition "on" (or "upon") when followed by a noun or gerund phrase, or used with a subclause beginning with "that" (e.g., "insisted that staff complete...").

Corrected Sentence:
"The director insisted on staff completing the audit even though several employees weren’t ready to begin the work." or "The director insisted that staff complete the audit even though several employees weren’t ready to begin the work."