用于处理电梯受困的装置有（）.
A.限速器
B.警铃
C.缓冲器
D.限位开关
参考答案：B
用"are"或"is"填空。
1. There __________ three pencils and a pen in my pencil-box.
2. There __________ many kites in the sky.
3. There __________ a pen and two rulers on your desk.
4. There __________ a pencil-case in my bag.
5. There __________ two end tables near the bed.
6. There __________ some fish in a river.
质坚体重，断面可见棕色环和油点，气香浓烈的是（）
A.防己
B.木香
C.川木香
D.川贝母
E.远志
