单项选择题
A.弦向干缩 B.纵向干缩 C.径向干缩
A.越短 B.越长 C.不变
A.2%-5% B.5%-8% C.8%-10% D.10%-12%
A.1/4-1/3 B.1/3-1/2 C.1/2-2/3 D.2/3-3/4
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