三家德国企业欲在中国设立一家有限责任公司,他们应到( )办理登记手续。
A.省级工商机关
B.市级工商机关
C.县级工商机关
D.国家工商行政管理局
参考答案:D
When help,one often says" Thank you,"or" It's kind of you." [ ]
A. offering
B. to offer
C. to be offered
D. offered
若单项式3x2y5与-2x1-my3n-1 是同类项,则mn=( )。