＿＿can you find out how many chickens there are!

A．Counting them

B．By counting them

C．Only by counting them

D．Only have you counted them

在阳离子H₂S分组方案中，下面（）都是Ⅱ组离子。

A.Hg2+，Pb2+，Cu2+

B.Fe3+，Ag+，Ca2+

C.Ca2+，Fe3+，Cr3+

D.Ag+，Ca2+，Mg2+