The conclusion isn’t that artists should convince other artists to apply for subsidies, it’s that artists, if able, should repay subsidies they receive.

It could be that artists should acknowledge that they succeeded because of factors other than merit, be very grateful for the help they got, and still not have a moral obligation to repay the subsidy. (B) doesn’t talk at all about when you have an obligation to repay a subsidy.

In other words, (C) says that if the source of a subsidy wants to be repaid and you have the ability to do so, then it is a debt you owe. We know from the stimulus that repayment would be “welcome”. Thus, (C) helps justify the idea that an artist is morally obligated to repay when they can.

The conclusion is about whether an artist has a moral obligation to repay a subsidy. (D) is instead talking about the process the government should use for granting subsidies.

The conclusion is about whether artists have a moral obligation to repay subsidies they receive — it’s not about the process for obtaining a subsidy. The argument doesn’t discuss how or when an artist should get a subsidy, just that if they do, they may be obligated to repay it.