During the nineteenth century, the French academy of art was

The stimulus describes an apparent discrepancy. The French academy discouraged innovation in the arts during the 19th century, and yet 19th century French painting showed a remarkable degree of innovation but sculpturing did not.
The question is why?
We can only guess at the reasons.
However the correct answer choice should be the one which would point to a critical difference between French painting and sculpture in the 19th century.

Answer choice (A) is the Opposite answer. If painting received more financial support than sculpture, we'd expect it to be less innovative given the artistic direction of the French academy. French painting, however, was apparently more innovative. Answer choice (A) deepens the paradox instead of resolving it.

Answer choice (B) is another an Opposite answer. The fact that more sculptors than painters were supported helps explain (to an extent) why sculpture was less innovative, assuming that each artist received a more-or-less equal share of this support. However, the second part of answer choice (B) states that individual painters received more support, on average, than individual sculptors. If so, we'd expect that that painting would be less innovative, not more.

Answer choice (C) is the correct answer choice. If there were a lot more unsponsored paintings than unsponsored sculptures, then no wonder 19th century painting showed a remarkable degree of innovation: more paintings than sculptures were produced without the auspices of the academy, which limited innovation.

Answer choice (D) is incorrect as it has no effect on the discrepancy we're trying to explain.

Answer choice (E) is incorrect, because the total amount of support received by the artistic community is irrelevant. Our job is to explain why painting was more innovative than sculpture, even though they are both art forms sponsored by the French academy. The correct answer choice must point to a material difference, not similarity, between these two art forms.