7.客车与货车从A、B两地同时出发,若相向而行,则客车与货车a小时后相遇;若同向而行,则客车b小时后追上货车,那么客车与货车的速度之比为( )
0 284614 284622 284628 284632 284638 284640 284644 284650 284652 284658 284664 284668 284670 284674 284680 284682 284688 284692 284694 284698 284700 284704 284706 284708 284709 284710 284712 284713 284714 284716 284718 284722 284724 284728 284730 284734 284740 284742 284748 284752 284754 284758 284764 284770 284772 284778 284782 284784 284790 284794 284800 284808 366461
| A. | $\frac{a+b}{a}$ | B. | $\frac{b}{a+b}$ | C. | $\frac{b-a}{a+b}$ | D. | $\frac{a+b}{b-a}$ |