评论
打印
答案：C
解析：
If x = a, then (x-a)(x-b)/(x-c) = (a-a)(a-b)/(a-c) = 0/(a-c) = 0. If x = b, then (x-a)(x-b)/(x-c) = (b-a)(b-b)/(b-c) = 0/(b-c) = 0. If x = c, then (x-a)(x-b)/(x-c) = (c-a)(c-b)/(c-c) = (c-a)(c-b)/0, which is not defined because division by 0 is undefined. Therefore, of the three values, a, b, and c, the only one for which function f is undefined is c. Thus the correct response is III only.
