在刨槽中,铜斑的缺陷如不清除,焊接时将会引起()。
A.热裂
B.夹铜
C.气孔
D.冷裂
参考答案:A
He has an expression of resentment, _____ Martin had made a fool of him.
A.as
B.as though
C.though
D.even though
用SQL语句建立表时为属性定义有效性规则,应使用短语______。
A.DEFAULT
B.PRIMARY KEY
C.CHECK
D.UNIQUE