A clean hand wants no washing. 身正不怕影子斜。
A clear conscience is a soft pillow. 问心无愧，高枕无忧。
A clear conscience is a sure card. 光明磊落，胜券在握。
A clear conscience laughs at false accusations. 白日不做亏心事，夜半敲门心不惊。
A clear fast is better than a dirty breakfast. 宁为清贫，不为浊富。
A close mouth catches no flies. 病从口入，祸从口出。
A cock is valiant on his own dunghill. 夜郎自大。
A common danger causes common action. 同仇敌忾。
A constant guest is never welcome. 久住非佳宾，常来不欢迎。
A contented mind is perpetual feast. 知足常乐。
A covetous man is good to none but worse to himself. 贪婪的人对别人毫无好处，对自己却坏处更大。
A crafty knave needs no broker. 狡猾的流氓，不需居间人。
A creaking door hangs long on its hinges. 户枢不蠹。
Action is the proper fruit of knowledge. 行动是知识的巧果。
Actions speak louder than words. 事实胜于雄辩。
A discontented man knows not where to sit easy. 不满足者坐无宁时。
A disease known is half cured. 病情确诊断，治病好一半。
Admonish your friends in private, praise them in public. 在私底下要忠告你的朋友，在公开场合又表扬你的朋友。