接触器自锁控制线路不但能使电动机连续运转,而且还具有欠压和()保护作用。
A.过电流
B.失压
C.过电压
D.过热
参考答案:B
看图完成对话。
1. A: Where are my keys?
B: Are they on the sofa?
A: , they .
2. A: Where are my pencils?
B: They're on the .
3. A: Where are the books?
B: Are they on the shelf?
4. A: Where's the phone?
B: It's on the .
能阻断α1和α2受体的药物是()能阻断β1和β2受体的药物是()
A.阿托品
B.哌唑嗪
C.普萘洛尔
D.酚妥拉明
E.美托洛尔