This is an illness that can result in total blindness left untreated. A. after B

This is an illness that can result in total blindness ____ left untreated.

    A. after          B. if            C. since         D. unless

试题答案

B

解析:

if left untreated意为“假如不进行任何治疗”。that can result in total blindness是定语从句修饰illness。