经济学人下载:四条腿朋友的代价 粪量变能源

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例句:She always said I ought to live alone.
她总说我应该一个人住。 

2.clean up 清理

例句:I cleaned myself up a bit, and got the baby ready.
我拾掇了一下自己，把宝宝也收拾妥当。

3.pick up 捡起；获得

例句:Where did you pick up your English?
你在哪儿学的英语？

4.at a cost of 花费；...的代价

例句:The new shopping centre was constructed at a cost of 1.1 million.
新的购物中心耗资110万建成。