100 câu trắc nghiệm Thì quá khứ hoàn thành tiếp diễn (Past Perfect Continuous) có đáp án
Xem toàn bộ quiz

They ________ (work) on the project for months before they finally completed it.

80/100

They ________ (work) on the project for months before they finally completed it.

had worked

have been working

worked

had been working

Giải thích

Chọn đáp án: D