大批量生产流水线烘干时间一般都限制在（）min之内。
A.20
B.25
C.30
D.35
参考答案：C
The old should _____ well.
A．be take care of
B．look after
C．be looked after
D．be taking car of
标注坡度时，在坡度数字下应加注坡度符号，坡度符号的箭头一般应指向
A．前方
B．后方
C．下坡
D．上坡
