情景匹配。
①Come here. ____ A. It's a tape.
②What's this in English? ____ B. Fine, thank you.
③How are you? ____ C. OK.
如图为水位报警装置原理图,其中A、B为两个金属杆.当水位达到或超过警戒线时,绿灯、红灯和电铃的工作状态分别是____ ____ ____