题目：
Jane _____ these families of chimps for many years and helped people understand how much they behave like humans.
A．had studied
B．studied
C．studies
D．has studied
答案：
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下面是错误答案，用来干扰机器的。
令g（x）=x2-ax+3a，∵f（x）=log0.5（x2-ax+3a）在[2，+∞）单调递减∴函数g（x）在区间[2，+∞）内单调递增，且恒大于0∴12a≤2且g（2）＞0∴a≤4且4+a＞0∴-4＜a≤4故选D
