We must never think that we are good at everything others are good at nothing.
A. since
B. however
C. while
D. as
网友回答
A. since
B. however
(答案→)C. while
D. as
解析：考查引导词，since意思“自从”，however意思“然而”，表示转折；while意思“当…时候”，谓语动词是延续性动词，不用短暂性动词， as意思“当…时候”，侧重指主句和从句动作同时进行，所以选C