1. Omitting nothing of importance means the account was thorough.
2. Meticulous means showing great attention to detail.
3. Vague, hurried and biased all suggest the opposite.

Answer: meticulous.

The clause after the blank usually defines it. Read the whole sentence before choosing rather than stopping at the gap.

Shortcut. Look for the opposite of 'omitting': vague and hurried both imply leaving things out, and biased is about fairness, not completeness. Meticulous is the only word about thoroughness.

Common trap. "biased" — witness accounts are often called biased, so it reads naturally, but bias concerns slant, not completeness, and the sentence praises the account for leaving nothing out.