问题
单项选择题
Most environmental problems exist because adequate measures for preventing them______ in the past.
A．was not taken
B．were not taken
C．didn't take
D．haven't taken
答案
参考答案：B
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Most environmental problems exist because adequate measures for preventing them______ in the past.
A．was not taken
B．were not taken
C．didn't take
D．haven't taken
参考答案：B