简述煮炉的合格标准。

My father _____________ go to work by bike. He goes on foot. [ ]

A. does

B. don't

C. doesn't

"What's he doing for vacation? He's _________ at home, and he's feeling _________." [ ]

A. relaxing; relaxed

B. relaxed; relaxing

C. relaxed; relaxed

下图所示电路中，对负载电阻R_L而言，点划线框中的电路是否可用一个等效电源代替若可以，该等效电源是（）。

A．可以，该等效电源是理想电压源

B．可以，该等效电源是理想电流源

C．不可以等效

D．不能确定

一氧化碳中毒，可见

A．皮肤黏膜呈樱桃红色
B．皮肤干燥
C．皮下气肿
D．皮肤痰斑
E．皮肤潮湿