第一道——customize a bike by exchanging the front wheel for a wheel that had one half the diameter of the back wheel,then when ride the bike,how many revolutions does the front wheel make for each revolution of the back wheel?
C 2
D 1/2
第二道——When 15 is divided by the positive integer k,the remainder is 3,.For how many different values of K is the true?我觉得是4个（1,2,3,4）,但答案给的是3个,为什么,哪里错了?