As a saying goes, the wise man knows he knows nothing, the fool thinks he knows all.
A. when
B. while
C. as
D. though
网友回答
A. when
(答案→)B. while
C. as
D. though
解析：考查连词：A. when当…时候，B. while当,..时候，虽然，然而，C. as 因为，随着，正如，D. though虽然，句意：俗话说，明者知自之不知，愚者自认无所不知。这里while表示对比，选B。