问题
选择题
The elderly _________ good care of in public places like supermarkets and airports; they are likely to get lost.
A．can have been taken
B．ought to be taking
C．must be taken
D．should take
答案
答案：C
考查情态动词。句意：上了年纪的人必须在公共场合被很好的照顾，像超市和机场，他们很可能会迷路。故选C。
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纸上作出电珠的伏安特性曲线
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