Critical Reasoning

When the salesman in the guitar department of a music store plays an electric guitar in the showroom, he sells more guitars than when he plays a classical guitar. The music store gives the salesman a 5% commission for every guitar that he sells. It can be concluded that the salesman enjoys playing on an electric guitar more than he does on a classical guitar.

The above conclusion is properly drawn if which of the following is assumed?

A: The number of guitars sold could be increased if there were seperate showrooms for electric and classical guitars.
B: The salesman's enjoyment as a guitarist is based only on the amount of money he earns by playing.
C: The salesman's commission is higher than that offered by most music stores.
D: An electric guitar is a far more versatile instrument than a classical guitar.
E: The skills needed to play an electric guitar are slightly different to those needed to play a classical one.

Source : Master Gmat.
Request: Kindly support your choice with explanation.