词性变化
1. origin.n.-adj. original 2. devote.v. –n. devotion-adj. devoted 3. respond.vi. –n. response ....
at one time（=once） “从前、曾经”。at times（=sometimes）“有时、间或”.at all times（=always） “一直、随时”。at a time（=each time）“一次、每次”。
at no time “在任何时候都不、绝不”。 at the same time “同时”/然而。
for a time “一度、一段时间”,相当于 for some time
....
1. Should we take this boy away from the bad e__________ influences(影响) in which he lives?
2. I take care of our neighbor’s dog while they are taking a three-week t________ of Europe.
3. All of us should work hand in hand to prevent the endangered s________ from dying out
....