he has been blind since birth Joseph Chadbourne never feels different from his class-ma

问题补充：

he has been blind since birth, Joseph Chadbourne never feels different from his class-mates at school.

A. Since

B. Once

C. Unless

D. While

答案：

A. Since

B. Once

C. Unless

(答案→)D. While

解析：考察连词辨析。A既然；自从；B一旦；C除非，如果…不…；D尽管；当…时；然而；句意：尽管出生时就看不见了，但是Joseph Chadbourne从未感觉到自己与学校的同学有什么不同。根据句意说明D正确。考生要特别注意连词的一词多义现象。