请教一题

grasses

新东方模考光盘上的：
If △ represent one of the operations +, -, and *, is K△(l+m)=(k△l)+(k△m) for all numbers k, l, and m?
(1)k△l is not equal to l△k for some numbers k;
(2)△represent subtraction.
答案是D，我选B，(1)为什么可以？有什么反例？

hopr999

（1）告诉你△只能代表减号哦！