喷油的修复方法不适合于下列哪个零件()
A.曲轴
B.凸轮轴
C.活塞
D.不稳定
参考答案:C
"Grateful"means ________. [ ]
A. unhappy about something
B. disappointed because of something
C. pleased about something good that has happened,or something bad has not happened
在SELECT-SQL语言中,______子句相当于关系中的投影运算。
A.WHERE
B.JOIN
C.FROM
D.SELECT