Mark the letter A, B, C, or D to indicate the sentence that best combines each pair of sentences in the following questions. The fire-fighters made every effort to put off the flames. The building burned down completely. 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.