A.15倍直徑長度內斷絲超過10% B.10倍直徑長度內斷絲超過10% C.10倍直徑長度內斷絲超過5% D.8倍直徑長度內斷絲超過5%
A.5 B.6 C.7 D.8
A.80d2 B.60d2 C.120d2 D.100d2