Joy _______ as a language teacher in China for two years before she went back to London.

A．had worked

B．was working

C．worked

D．has worked

失代偿性呼吸性酸中毒时，血气分析及血清电解质的改变是（）

A.PaCO₂升高、pH升高、血钾升高

B.PaCO₂升高、pH降低、血钾升高

C.PaCO₂升高、pH降低、血氯升高

D.PaCO₂升高、pH升高、血氯降低

E.PaCO₂升高、pH升高、血氯血钾正常