--- How cool the iPhone5 is !

---In our shop it_____ very well now. Get one before it________out.

A． sells; sells

B．sells; is sold

C．is sold; is sold

D．is sold; sells

以下几种运行工况会降低锅炉效率（）。

A、低负荷

B、超负荷

C、负荷急剧变动

D、稳定负荷