— Mr. Lee to a student when I entered the classroom this morning.-- He is very patient he

问题补充：

— Mr. Lee to a student when I entered the classroom this morning.

-- He is very patient he is young.

A. talking; but

B. talks; though

C. was talking, though

D. talked, however

答案：

A. talking; but

B. talks; though

(答案→)C. was talking, though

D. talked, however

解析：but但是；though虽然，尽管；however然而，可是。句意：今天上午当我进入教室时，李老师正在对一个学生谈话。——尽管他年轻，但是他非常有耐心。结合语境可知上文描述的是过去某时正在进行的动作，故用过去进行时态，主语Mr. Lee是单数第三人称，故助动词用was。结合语境可知选C。