A) She is quite well now, except a slight cold.
B) She is quite well now, except having a slight cold.
C) She is quite well now, except for a slight cold.
Among the 3 sentence given above B sounds the best in conveying the meaning but is it grammatically correct/incorrect to use sentence A ? What about sentence C ? It too sounds better than A in conveying the meaning but not as good as option B but again is it correct / incorrect ?