A:CoCl
B:CoCl2
C:CoCl3
D:CoCl4
四瓶失去标签的溶液分别为①NaCl ②CuSO4③BaCl2④H2SO4不用任何试剂将它们一一检验出来的正确顺序是( )
He is very serious. No one can make him___.
已知2x6y2和-13x3myn是同类项,则2m+n的值是( )