According to a new sociological theory, artists and musicians excel in their chosen field of endeavor only if they are naturally gifted or extremely diligent about practicing. In order to have time to be materially successful in one's professional life, the author of the theory claims, one must not undertake a creative pursuit unless one is naturally gifted at it. This injunction makes many assumptions, but does not presuppose that ___________________.

A.professionals who spend a great deal of time practicing their creative pursuit will not earn much money.
This is indeed an assumption made by the author of the argument, who feels that there is not enough time to both spend a lot of time practicing in order to succeed creatively and spend the necessary time to succeed professionally.
B.only people who are naturally creatively gifted can succeed both creatively and professionally.
This is as much a summary of the argument as it is an assumption underlying it, but it counts as the latter in that it leaves out some of the intricacies of the stem text.
C.a person cannot succeed professionally and succeed creatively at the same time.
[spoiler]This is the credited response. Don't be fooled by the word "time" here: the author accounts for the possibility that one might be so naturally gifted as to be able to work hard professionally and be creatively successful without having to devote time to practicing. [/spoiler]
D.time spent practicing a creative endeavor curtails one's ability to spend time pursuing professional success.
This is true according to the author.
E.one should not pursue a creative field unless one intends to excel in it.
[spoiler]This is hardly true, in that it ignores the simple joys of creative expression, but it can be said to be an important assumption for the author's argument, which takes the perspective that any pursuit worth undertaking is worth doing successfully.[/spoiler]