Hector’s argument is based on the idea that the public benefit should be pursued, and relies on equating what the public thinks is beneficial to what is truly beneficial. That’s possible even without following public opinion no matter what—this assumption is unnecessary.

Hector’s conclusion is phrased as a conditional, so it doesn’t depend on whether Monica’s assessment is accurate. It just wouldn’t be triggered if Monica’s assessment is inaccurate.

Hector isn’t concerned with the sculpture’s artistic merit, just whether it benefits the public. That makes this, like (D), both unnecessary and irrelevant.

Like (C), this is simply irrelevant, because Hector’s argument doesn’t involve whether or not the sculpture has artistic merit.

Hector infers that the public scorning the sculpture would mean the sculpture was not beneficial, on the basis that the public would not feel the sculpture was beneficial. This requires assuming that public feelings about the sculpture’s benefit actually indicate that benefit.