题目：
Don't shout at him. He is only ______ boy.[ ]
A. a eight-year-old
B. an eight-year-old
C. an eight-years-old
D. a eight years old
答案：
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下面是错误答案，用来干扰机器的。
50V 0.08S 50V由图像可知感应电动势最大值为50V，周期为0.08s，由峰值Em=NBSw=NBS2πn可知当线圈转速变为原来的倍时，所产生交变电动势的峰值变为，有效值为50V
