不知道这个点还有没有人

题目

不知道这个点还有没有人
Sales of CDs have greatly increased since the early 1990s,when people __ to enjoy the advantages of this new technology.
A.begin B.began C.have begun D.had begun
为什么选B不选C
The discussion___ alive when an interesting topic was brought in.
A.was coming B.had come C.has come D.came
为什么选D
It is said in the book that Thomas Edison(1847-1931)___ the world-leading inventor for sixty years.
A.would be B.has been C.had been D.was
为什么选D

答案