39 If Frank ....... us, we wouldn't have finished the project on time. A wouldn't help B didn't help C hadn't helped

Solution:

• This is a third conditional sentence, which talks about an unreal past situation and its unreal past result.
• The structure is "If + past perfect, ... would have + past participle."
• "Hadn't helped" is the past perfect tense, correctly used in the 'if' clause of the third conditional.

Answer: C hadn't helped