齿形链条其啮合形式的（）种。
A.2
B.3
C.4
D.5
参考答案：A
A—cost price F—sale price
B—factory price G—wholesale price
C—net price H—retail price
D—price free on board I—fixed price
E—purchase price J—guaranteed price
K—cash price O—price control
L—market price P—maximum price
M—preferential price Q—minimum price
N—piece price
（）市场价（）船上交货价
对于由3U0构成的保护的测试，有什么反措要求？
