1 . 当你网购时，在保证安全方面你有其他好的建议吗？（省略句）
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2 . when/while doing...
学习一门外语时，我们需要的是更多的练习。(汉译英)

3 . 到达目的地后，我们就开始观光了。(sightseeing) （汉译英）

4 . Professor Smith, here is an article I’ve just written, will you please read it through and correct the mistakes, ________?

A．if any

B．if some

C．if so

D．if not

5 . While riding in the street, ________.

A．someone called me from behind	B．my bike broke down
C．I heard my name called	D．an old man knocked down