Richard, ________, works in isolation but I have no doubts about his abilities.A. on instanceB. as instanceC. for instance

步骤 1：理解句子结构
句子结构为“Richard, ________, works in isolation but I have no doubts about his abilities.”，其中“Richard”是主语，“works in isolation”是谓语，“but I have no doubts about his abilities”是并列句。空格处需要填入一个插入语，引出“Richard”作为例子。
步骤 2：分析选项
A. on instance：不符合英语习惯用法。
B. as instance：不符合英语习惯用法。
C. for instance：意为“例如”，可作插入语，引出“Richard”作为例子。
步骤 3：验证答案
将“for instance”代入原句：“Richard, for instance, works in isolation but I have no doubts about his abilities.”，语义通顺且符合要求。