【答案】Although he is very old, _________ he works very hard.

Although he is very old, _________ he works very hard.

A. and B. but C. / D. so

【答案】

C

【解析】

句意：尽管他很老了，但是他工作非常努力。在让步状语从句中，如果用although，则不用but。据题意，故选C。