在等速运行时，若测速回路失压或断线，JSJ没有吸合，便断开（）实现紧急制动。
A.控制回路
B.测速回路
C.励磁回路
D.安全回路
参考答案：D
选择恰当的答语。
A. I'm ten.
B. Great !
C. Sure! Here you are.
D. Thank you!
E. Nine!
( )1. Happy birthday to you!
( )2. How many cars?
( )3. How old are you?
( )4. May I have a look?
( )5. Let's eat the birthday cake!
–What colour is _____ pen? –It’s black.
A. a B. an C. the
