| cognizant(familiar, careful, knowledgeable, aware, informed) |
| common(pleasant, fair, agreeable, suitable, adequate) |
| complete(decent, knowledgeable, adequate, qualified, capable) |
| comprehending(alert, intelligent, attentive, watchful, sharp-eyed) |
| concentrated |
| conscientious(adjective, careful, caring, thoughtful, knowledgeable) |
| considering(alert, intelligent, attentive, watchful, sharp-eyed) |
| contemplating(alert, intelligent, attentive, watchful, sharp-eyed) |
| conversant(familiar, careful, knowledgeable, aware, informed) |
| cooking with gas(expression, idiom, fair, agreeable, proper) |
| cool(adjective, smooth, pleasant, moderate, appropriate) |
| copacetic(cool, pleasant, fair, big, agreeable) |
| correct(adjective, right, exact, alert, intelligent) |
| crack(adjective, smooth, smart, clean, practical) |
| crafty(adjective, good, smooth, keen, sharp) |
| crisp(decent, knowledgeable, adequate, qualified, capable) |
| cunning(adjective, smooth, keen, sharp, smart) |
| dead on(expression, right, perfect, exact, proper) |
| decent(pleasant, fair, agreeable, suitable, adequate) |
| deducing(alert, intelligent, attentive, watchful, sharp-eyed) |