一个因数的末尾有两个0,另一个因数末尾没有0,积的末尾至少有[ ]
A.2个0
B.3个0
C.1个0
D.2或3个0
答案:A
Jack wasn’t saying anything , but the teacher smiled at him_____he had done something very clever.
A.as if
B.in case
C.while
D.though
用横向磨削法磨削平面时,磨削宽度应等于横向进给量。