测量径向孔夹角角度,要先在()径向孔插入无间隙芯轴,然后用圆柱、千分尺进行测量。
A.一个
B.两个
C.三个
D.四个
参考答案:B
有两列火车,一列长102米,每秒行20米;另一列长83米,每秒行17米。两车在双轨线上相向而行,从两车相遇到车尾离开一共用了( )秒。
根据所给情景选择最佳答案。
当你想问别人花瓶里有多少枝花时,可以说[ ]
A. How many flowers are there in the vase?
B. How much flowers are there in the vase?
C. What colour are the flowers?