单选题 ______, glasses can correct most sight defects in healthy eyes.
A. When well-fitted B. If well-fitting
C. When well-fitting D. If well-fitted when

【正确答案】 A
【答案解析】[解析] 分词用法题。本句中分词与句子主语构成动宾关系，故应用过去分词，四个选项中只有A正确。