It is very difficult for pedestrians to know how fast a car is traveling.
问题描述：
It is very difficult for pedestrians to know how fast a car is traveling.
答
行人很难得知一辆车正行驶的有多快
答
人行道上的行人很难知道汽车跑得多快
答
行人很难知道行驶中的汽车有多快