Câu hỏi: Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines the pair of sentences given in each of the following questions.

A. The building burned down completely though the fire-fighters made every effort to put off the flames.

B. Had it not been for the fire-fighters’ every effort, the building would have burned down completely.

C. Making every effort to put off the flames, the fire-fighters completely burned down the building.

D. Since the fire-fighters made every effort to put off the flames, the building burned down completely