单项选择题
A.10 B.11 C.12 D.13
A.1/4~1/2 B.1/5~1/3 C.1/5~1/2 D.1/8~1/4
A.摆线 B.渐开线 C.双曲线 D.抛物线
A.16 B.17 C.18 D.19
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