Humans can be attacked by many different parasites (many species of bacteria, viruses, fungi, flatworm, apicomplexan, etc). Is it reasonable to expect that most other species face a similar array of parasites?

Yes

Explanation:

Humans can be attacked by many microbes like bacteria, viruses, fungi, and parasites like flatworms, etc. These parasites and microbes cause different infections and diseases in humans.

This is true to most other species that they also face a similar array of parasite because every species represents a source which can be exploited by an array of parasites. Each parasite attacks on specific organs or tissue which allow different parasite to attack different organs. Therefore it is reasonable.

answer: b: experiments that showed that all cells are similar in how they metabolize and in their composition

explanation:

you can have just about every answer you can think of