单项选择题

A.Ⅷ:C和Ⅷ:Ag同时减低
B.Ⅷ:C减低,Ⅷ:Ag升高
C.Ⅷ:C增高,Ⅷ:Ag减低
D.Ⅷ:C减低,Ⅷ:Ag正常或偏高
E.以上均不是