Technically, this is known as an argument from silence, which is considered a relatively weak form of argument. Just because the accounts don't mention certain symptoms doesn't mean the Athenians didn't experience them. It's possible they did experience all the symptoms of Ebola, but the accounts that survive just happen not to mention these particular symptoms, for whatever reason. So the degree to which this answer choice weakens the argument depends on some assumptions about how significant these other symptoms of Ebola are, and whether they would have been likely to be recorded. But this does weaken the argument, even if very slightly.

The author never says that Ebola leads to hiccups in all cases, just that hiccups as a disease symptom are linked only to Ebola, among all known diseases. So this answer choice doesn't say anything that undermines the author’s argument.

If this is true, then even though the symptoms of Ebola match some of the symptoms described in accounts of the epidemic, there's no clear way for Ebola to have been in Athens at the time. This makes it seem less likely that Ebola, as opposed to some unknown disease, caused the epidemic.

By pointing out an important difference between Ebola and the disease that caused the Athenian epidemic, this answer choice makes it seem less likely that Ebola was the epidemic. This weakens the argument.

This answer choice also points out a difference between Ebola and the Athenian epidemic. Thus, it also weakens the hypothesis that Ebola caused the epidemic.