请教GWD一数学题

Q18:

Last year the price per share of Stock X increased by k percent and the earnings per share of Stock X increased by m percent, where k is greater than m.  By what percent did the ratio of price per share to earnings per share increase, in terms of k and m?

A.    k/m %

B.     (k-m) %

C.     [100(k-m)]/(100+k) %

D.    [100(k-m)]/(100+m) %

E.     [100(k-m)]/(100+k+m) %

正确Answer: D

拜托,多谢！