问题
选择题
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
答案：D
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。