Find the one mistake (A, B, C or D) in these sente...

Câu hỏi: Find the one mistake (A, B, C or D) in these sentences and then correct them: Last week (A) unless my mother (B) had had (C) enough money, she (D) would have bought that toy for me.

A. unless

B. had had

C. enough money

D. would have bought