Mark the letter A, B, C,...

Câu hỏi: Mark the letter A, B, C, or D to indicate the sentence that best combines each pair of sentences in the following question.

A. The teacher has done his best to help all student, then, none of them made any effort on their part

B. Although the teacher has done his best to help all students, none of them made any effort on their part

C. Because the teacher has done his best to help all students, , none of them made any effort on their part

D. If the teacher has done his best to help all students, , none of them made any effort on their part