房地产估价机构资质核准、房地产估价师执业资格注册均被列为行政许可项目； ( )

─By the way, where is Li Lei?

─ He ________ swimming. [ ]

A. has been

B. has been to

C. has gone

D. has gone to

易腐货物的变更有何规定？

听诊牛结肠频繁出现流水音，该牛可能患（）

A.瘤胃积食

B.肠炎

C.瘤胃阻塞

D.肠臌气

E.便秘

对计量经济模型的检验应从几个方面入手。 

焊接时选择焊接电流大小的依据是什么？