如：He became a teacher at (the age of) 17.
The weather became warmer.
Soon the room became crowded.
比如不说 Soon the room became crowded by students.
2. become 是终止性动词，因此要表示“成为…有多长时间”有多长时间，英语不能将become与表示一段时间的词或短语连用。
正：He became a teacher ten years ago.
正：It’s ten years since he became a teacher.
正：He has been a teacher for ten years.
误：He has become a teacher for ten years.
3. become 之后一般不接不定式表示“逐渐…” (此时可用 come, begin＋不定式)。如：＋不定式
正：He began [came] to like English. 他开始喜欢英语起来。
误：He became to like English.
正：He became ill yesterday. 他昨天病了。
误：He became to be ill yesterday.
4. 用于习语 become of, 表示“发生”、“遭遇”等 (常与 what连用)。
如：What has become of the girl?
I don’t know what will become of me if I fail this time.