清洗制动缸前要先装设（），插上安全销，卸除制动缸盖螺母时，头部要闪开。
A.安全链
B.安全钩
C.安全套
D.安全绳
参考答案：C
The old town has narrow streets and small houses _______ are built close to each other .
[ ]
A. in which
B. where
C. what
D. that
成文的制度
