机车制动时向轨面撒砂（）制动力。
A、可降低
B、可提高
C、不影响
参考答案：B
下列语句：①若直线a∥b，b∥c，则a∥c；②生活在水里的动物是鱼；③作两条相交直线；④∠A与∠B相等吗？其中是命题的有（ ）
A．1个
B．2个
C．3个
D．4个
My shoes are black. _________? [ ]
A. What colour is yours?
B. What about yours?
C. What about you?
D. What colour are your?
