A:Cu2+、OH﹣、SO42﹣
B:H+、Na+、HCO3
C:NH4+、H+、NO3﹣
D:K+、H+、MnO4﹣
The little girl could look after _________ though she was only five years old.
健康成年人,一次失血超过( )就会危及生命。