He failed the exam he tried his best.A. because B. though C. So

问题补充：

He failed the exam, he tried his best.

A. because B. though C. So

答案：

解析：句意为：虽然他尽力了，但是还是考试不及格。because：因为，though：虽然……但是……， So：因此。根据句意可知应选B。