Most environmental problems exist because adequate measures for preventing them_

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问题 Most environmental problems exist because adequate measures for preventing them______ taken in the past.

选项 A、was not
B、were not
C、were not being
D、being not

答案 B

解析被动语态的时态、数、性的一致，主要由助动词来表示，要注意它们与主语的一致。此处从句的主语measures是复数，因此选择答案B。

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Sheremainsconfidentand______untroubledbyourpresentproblems.A、indefinitely