It is not necessary for the ethicist to assume that doctors often do not know what is best for their patients. As long as they at least sometimes have gaps in their knowledge, his argument still stands.

Try negating this: patients’ knowledge that experimental treatments are being used couldn’t adversely affect the outcome of research. Patients might still refuse, or be incapable of consenting to, experimental treatments in the first place, though. In that case, the ethicist’s argument still stands. So (B) isn’t necessary for him to assume.

The ethicist is arguing in favor of nonconsensual research, and this provides a limitation on nonconsensual research. So this can’t be a necessary assumption of the argument.

This is too strong to be necessary, even assuming that these are the cases the ethicist is talking about. He doesn’t have to assume that patients lose their rights in all such cases; only that they sometimes do. Furthermore, his main concern is ignoring patients’ consent, which is not identical to denying them knowledge.

Negated, this is: the right of patients to informed consent in medical emergencies is never outweighed by the possible benefits of nonconsensual research. If so, the author’s argument for nonconsensual research collapses. Consequently, he must assume that (E) is true.