1.up to 忙于；目的是...

例句：What are they up to?
他们安的是什么心?

2.lock up 关闭；封锁

例句：Don't forget to lock up when you leave.
你离开时不要忘记上锁。

3.mend one's ways 使...改邪归正

例句：He was determined to mend his ways and turn over new leaf.
他决心改过自新,重新做人。

4.one at a time 一次一个
例句：Wouldn't it taste better if you bought one at a time?
如果你一次买一杯，味道不是更好些吗？