鼻腔毛细血管瘤最常见于（） A.上鼻甲前端和鼻中隔上部 B.中鼻甲前端和鼻中隔上部

The Science Museum, ________ we visited during a recent trip to Britain, is one of London’s tourist attractions.

A．which

B．what

C．that

D．where

The sales manager of the company suggested more money is to spent in a more effective advertising campaign and better packaging design.

A．is spending on

B．will be spent in

C．will be spent on

D．be spent on

下列选项中属于双端的带隔离的直流-直流变流电路的是（）。

A.半桥电路

B.全桥电路

C.推挽电路

D.正激电路

PNP三极管工作特点是（）.

A．发射区发射电子，集电区收集电子

B．发射区发射空穴，集电区收集电子

C．发射区发射电子，集电区收集空穴

D．发射区发射空穴，集电区收集空穴