While some of the candidates performed well in this question to score high marks others did not.  They even goofed by claiming that violin and guitar are the same in appearance.

Some of the expected answers are:

(a)Similarities:
Both are string instruments 
Both have finger boards
Both have bridge

Differences:
            Violin is a Western classical orchestra instrument while guitar is not. 
            Violin uses the bow while guitar does not.   
            Guitar cannot be bowed whereas violin can.

(b)     Viola, Cello and Double bass.