电动机的引出线和电缆头以及外露的转动部分均应装设牢固的_____。
参考答案：遮栏或护罩
—______ bread would you like?
—Three pieces of ______.[ ]
A．How many, breads
B．How many, bread
C．How much, breads
D．How much, bread
光缆型式由（）部组成。
A.4
B.5
C.6
D.7
