Our math teacher in our school for 20 years and he here when he was 23 years old.A. has

问题补充：

Our math teacher in our school for 20 years and he here when he was 23 years old.

A. has taught, has come

B. taught, comes

C. taught, came

D. has taught, came

答案：

A. has taught, has come

B. taught, comes

C. taught, came

(答案→)D. has taught, came

解析：考查动词的时态。for 20 year是现在完成时的时间标志。因此第一空要填has taught；后半句时间状语是when he was 23 years old，动词用一般过去时，因此天came.故答案为D。