单选题：How many cities will have air quality monitoring systems ins

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题目内容：

How many cities will have air quality monitoring systems installed by the end of this year?
[A] 42 cities.
[B] 220 cities.
[C] 150 cities.
[D] 262 cities.

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根据材料，请在（1）处填上最佳答案。

分类：专四题型：单选题

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