:
延续动词用于肯定句，表示"做……直到……" 瞬间动词用于否定句，表示"到……，才……"。例如：
He didn't come back until ten o'clock. 他到10 点才回来。
He slept until ten o'clock. 他一直睡到10点。
典型例题
1. You don't need to describe her. I ___ her several times.
A. had met B. have met C. met D. meet
答案B. 首先本题后句强调对现在的影响，我知道她的模样，你不用描述。再次，several
times告知为反复发生的动作，因此用现在完成时。
2. ---I'm sorry to keep you waiting.
---Oh, not at all. I ___here only a few minutes.
A. have been B. had been C. was D. will be
答案A. 等待的动作由过去开始，持续到现在，应用现在完成时。
