My brother worked hard. He passed the test.

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.
My brother worked hard. He passed the test.
A. My brother worked hard because he passed the test.
B. If my brother hadn't worked hard, he wouldn't have passed the test.
C. Unless my brother worked hard, he passed the test.
D. He passed the test, so he worked hard.