This is an illness that can result in total blindness if. A. to leave untreatingB. left un

问题补充：

This is an illness that can result in total blindness if.

A. to leave untreating

B. left untreated

C. leaving untreating

D. is left untreated

答案：

A. to leave untreating

B. left untreated

C. leaving untreating

D. is left untreated

解析：状语从句的省略形式，其完整形式是： ... if it is left untreated.