He regretted the days __ he wasted in the woods and __ he should have studied.

He regretted the days __ he wasted in the woods and __ he should have studied.
A.when;when
B.that;when
C.when;that
D.that;that
答案是B
为什么？不能选C？
请详细说明。

The moment he had said this,he regretted it. He regretted the days __ he wasted in the woods and __ he should have studied. He is now in the pen.He regretted having done that. Mr. John regretted ___ his secretary for the mistake , for he later discovered it was his own fault He was born ____the morning of december 8th 1 The doctor ___on th patient presently: he has yet prepared himself for the operation I regretted saying it almost at once th%是什么意思？ A young man was swimming the river. He saw a fat man in th w------- near bank looking at a big dog. 24th中的th全称是什么？