某减速机的大小齿轮的直径分别为100cm、20cm,该减速机的减速比是5?
参考答案:对
-The ground is wet.
-It must have rained last night,_____? [ ]
A. hasn't it
B. didn't it
C. mustn't it
D. isn't it
印度最大的港口和棉纺织工业中心是( )
A.加尔各答
B.班加罗尔
C.孟买
D.新德里