捷克教育家夸美纽斯说过：“教师的嘴是一个源泉，从那里可以产生知识的溪流。”这指的是教师的( )。

A. A Winner’s Secret
B. A Winner’s Problem
C.A Winner’s Opportunity
D. A Winner’s Achievement

A. excuses for their failures
B. barriers to greater power
C. challenges to their colleagues
D. chances for self-development