柴油发动机排气冒黑烟是因为（）。
A.发动机水温太高
B.喷油时间太迟
B.柴油中有水分
D.发动机上机油
参考答案：B
Mr.Green told us ____ too much time ____ reading novels. [ ]
A. don't take; on
B. not to take; in
C. not to spend; in
D. don't spend; on
两条直线被第三条直线所截，则[ ]
A．同位角一定相等
B．内错角一定相等
C．同旁内角一定互补
D．以上结论都不对
