选择热继电器时，应根据被控设备的（）来选择相应发热元件的规格。
A、额定电流
B、额定电压
C、额定效率
D、额定功率
参考答案：A
Directions: Write an essay of 160--200 words based on the following drawing. In your essay, you should
1) describe the drawing briefly,
2) explain its intended meaning, and
3) support your view with an example/examples.
You should write neatly on ANSWER SHEET 2.
因式分解结果为-（2a+b）（2a-b）的多项式是（ ）
A．4a2-b2
B．4a2+b2
C．-4a2-b2
D．-4a2+b2
