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)&

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.