啮合传动不包括()。
A.齿轮传动
B.链传动
C.蜗杆传动
参考答案:A
若代数式2x2+3x+7的值是8,则代数式2x2+3x﹣7的值是[ ]
A.2
B.17
C.﹣6
D.﹣1
What does salt water draft mean?().
A.It means summer draft
B.It means maximum draft
C.It means fresh water draft
D.It means seawater draft