a. is fine. I've never heard 'sharp of hearing' but I suppose in context I'd understand what it means. Where did you see or hear that? From a native speaker?
Thanks. I've never heard or seen b either. I made it up myself.
Would it work 'He has a good ear'?
Would it work 'He has a good ear'?
Would [STRIKE]it work[/STRIKE] 'He has a good ear' work?