Mark the letter A, B, C, or D on...

Câu hỏi: Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions.
They finished one project. They started working on the next.

A. Had they finished one project, they would have started working on the next.

B. Only if they had finished one project did they start working on the next.

C. Hardly had they finished one project when they started working on the next.

D. Not until did they start working on the next project then they finished one.