— Wow! It snowed last night. What a nice world!

— You're right. But it's more difficult to find my missing keys with snow________ the ground.[      ]

A. covered  

B. cover

C. to cover  

D. covering

男6个月，咳嗽1周伴发热1天。查体：呼吸60次/分，口周青紫，双肺闻中小水泡音，心率180次/分，肝肋下5cm，胸片：双下肺模糊片影，心胸比例0.65。

首选的化验检查

A．肺功能＋血气分析

B．心电图＋血气分析

C．腹部B超＋心电图

D．痰培养＋血培养

E．肺功能＋痰培养