| astern |
| astute(adjective, reasonable, rational, sober, wise) |
| attending |
| attentive(adjective, reasonable, rational, intelligent, sober) |
| au courant(expression, adjective, reasonable, rational, intelligent) |
| aware(adjective, reasonable, rational, intelligent, sober) |
| back |
| behind |
| believable(adjective, sound, sensible, rational, intelligent) |
| by-product |
| canny(adjective, reasonable, rational, intelligent, sober) |
| cerebral(adjective, sound, reasonable, sensible, rational) |
| clear(sound, reasonable, sensible, rational, logical) |
| clear-cut(adjective, sound, sensible, rational, intelligent) |
| cogent(clear, sound, reasonable, sensible, rational) |
| cognitive(adjective, sound, reasonable, sensible, rational) |
| cognizant(adjective, reasonable, rational, intelligent, sober) |
| coherent(clear, sound, reasonable, sensible, rational) |
| coming |
| compelling(clear, sound, reasonable, sensible, rational) |