离心泵的滑动轴承合金层与轴承衬应结合牢固，合金层表面没有（）等缺陷。
A.气孔
B.夹渣
C.裂纹
D.剥离
参考答案：A, B, C, D
Prices ______ all the time. It's no wonder that we've spent so much money recently.
A．rose
B．had risen
C．were rising
D．have been rising
在唾液腺中分泌管最长的是（）
A.腮腺
B.颌下腺
C.舌下腺
D.唇腺
E.颊腺
