道路图中，设计路侧石线一般用（）画出。
A、红线
B、双点划线
C、粗虚线
D、图例
参考答案：C
若双曲线的焦点到相应准线的距离为P,离心率为e,则双曲线的实半轴长为__________.
Mr Johnson _______ a child at the start of the 1950s. [ ]
A. is
B. are
C. was
D. were
