请教：
if x and y and intergers, what is the remainder when x is divided by y?
1.when x is divided by 2y, the remainder is 4
2.when x+y is divided by y, the remainder is 4
答案是B.
由1. 推出x=2yA+4，--〉x=(2A)y+4，--〉x被y除，余数是4
由2. 推出x=(A-1)y+4，--〉x被y除，余数是4
因此1和2 都充分，应该选d?? | 
