题干
The students wanted to know ___________.
A：whether light goes faster than sound
B：how many colors were there in a rainbow
C：that the moon travels around the earth
D：what would the world be like in the future
答案(点此获取答案解析）
A
（其中0≤t≤20）给出，F（t）的单位是辆／分，t的单位是分，则在下列哪个时间段内车流量是增加的 （ ）