Mark the letter A, B,

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

A. Unless he had worked hard, he would have failed the exam. 

B. Even though he failed the exam, he didn’t work hard. 

C. If he had worked hard, he would have passed the exam. 

D. However hard he worked, he failed the exam.