Not necessary, because the author’s reasoning is based on the cost of getting regulatory-agency approval. The author doesn’t rely on purported ineffectiveness of herbs as part of the support for her conclusion.

Not necessary, because the argument is directed toward proving that licensed physicians can’t recommend herbs as medicine. But whether people can properly use a drug is not at issue; the author never argues that it’s improper for people to use unprescribed drugs. What matters is what licensed physician can or cannot do, not takers of drugs.

Necessary, because if it were not true — if a licensed physician CAN recommend the medicinal use of an herb even if it’s not offered for sale as a drug — then the premises no longer give us a reason to think licensed physicians can’t recommend herbs as medicine. Sure, the premises may establish that the herbs can’t be offered for sale; but doctors might still be allowed to recommend illegal herbs. So the author must assume this possibility isn’t true.

Not necessary, because the argument is concerned with proving that herbs can’t be recommended by doctors. But the author does not try to prove anything about substances besides herbs.

Not necessary, because the author never describes the cause of the high expense for regulatory approval. We don’t know if it has anything to do with the time it takes to get approval.