The most often used application of the term virtuosity applies to music - a virtuosic piece, a virtuosic musician etc. Thus the answer to this is b. Virtuosity means extreme technical proficiency in an area of music (though it can be applied to other things as well to show mastery of a skill - a virtuosic painter etc.)
Answer: The subject of this piece is the four figures standing on the beach. The content of the mood reflected by the colors and the musical qualities and movement reflected in the brushstrokes.
