Question

Three years had gone by ____ he came to realize what a fool he was not to listen to the teachers !

A．until

B．since

C． before

D．after

Answer 1

C

考查连词，until 直到，since 自从，before 在什么之前， after在什么之后，句意：自从他意识到多么的愚蠢呀他没有听老师的话三年已经过去了。所以选C。