要使三极管具有正常的电流放大作用，必须在其发射结上加（）偏置电压，在集电结上加反向偏置电压。
A、正向
B、反向
C、平衡
D、相等
参考答案：A
_______ with what the students had done, the teacher praised them highly.[ ]
A. Delight
B. Delighting
C. Delighted
D. Being delighting
句型转换。
1. She sings very well. (改为同义句)
She is _____ _____ singing.
2. Peter does some housework on Sundays. (改为否定句)
Peter _____ _____ any housework on Sundays.
3. Millie sometimes flies kites with her cousin in the afternoon. (改为一般疑问句)
_____ Millie sometimes _____ kites with her cousin in the afternoon?
4. Kitty goes to the Dancing Club once a week. (对画线部分提问)
_____ _____ does Kitty go to the Dancing Club?
5. My parents go to work by bus every day. (改为同义句)
My parents _____ a _____ to work every day.
