非正常验收有四种形式:返工更换验收、检测鉴定验收、设计复核验收、加固处理验收。其中,两种以上情况不能满足要求的即可拒绝验收。( )
参考答案:错
Some students often listen to music ___ ___ classes to refresh themselves.[ ]
A. between
B. among
C. over
D. during
油泵变频频率的正常范围为()。
(A)小于15Hz
(B)20~50Hz
(C)30~50Hz
(D)60Hz