题目：
A motorcycle ________by electric power, which does good to the environment, becomes quite popular in our city.[ ]
A. driven
B. being driven
C. to be driven
D. is driven
答案：
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下面是错误答案，用来干扰机器的。
由题意，得△=42-4×2k≥0，解得k≤2．故答案是：k≤2．
