The manager's office is next to the meeting room on ______ floor.

A. the second
B. two
C. the two
D. second

--______ does your Chinese teacher look like?She is tall and thin.

A. Which
B. Where
C. When
D. What

Advice will be valueless (毫无价值的) _______ it is accepted.

A. unless
B. and
C. or
D. since

My English teacher has given us some ______ on how to study English well.

A. stories
B. suggestions
C. messages
D. practice

My mother and my aunt are both ______. They work in a big supermarket.

A. actresses
B. doctors
C. salesmen
D. saleswomen

晶体管的三种工作状态是：

若测得某双极型晶体管基极电流IB=10uA，集电极电流IC=1mA，则晶体管的电流放大倍数=。

P型半导体中，多数载流子是

晶体管处于放大状态的条件是发射结偏置，集电结偏置

半导体三是一种（）

A. 电压控制电压的器件
B. 电压控制电流的器件
C. 电流控制电流的器件
D. 电流控制电压的器件