Like (D), the author never addresses how much artists are paid. Instead, he takes issue with the fact that their pay depends on subjective evaluations of their work. He also never argues that people should choose careers solely on this basis, just that it’s a relevant factor.

The author argues that it’s unacceptable for one’s pay to depend on subjective evaluations of one’s work. But he never makes any assumptions about what those subjective evaluations might be. He doesn’t assume that a work of art will be considered beautiful by everyone or no one.

In order to argue that one should avoid a career in art because it's unacceptable for pay to depend on subjective evaluation, the author must assume that pay in other careers isn't also based on subjective evaluation. But if it is, why should one choose a career other than art?

Like (A), the author never makes any claims or assumptions about how much artists are paid. Even if all artists are paid very well, this doesn’t change the fact that their pay is determined by subjective evaluations of their work, which the author claims is unacceptable.

This is the cookie-cutter flaw of confusing necessary and sufficient conditions. The author doesn't make this mistake. He doesn't present any criteria that are necessary for a “good” career. He only says that it’s unacceptable for pay to be determined by subjective evaluation.