tea antioxidants

The question is testing SUBJECT/VERB AGREEMENT.

If you see a split between singular and plural verbs in the answer choices, such as "comes" v. "come," you first must determine the subject.

Usually, when we have a collective noun or indefinite pronoun followed by a prepositional phrase, it is singular. For example, all of the following would be singular:
The group of students is
The board of directors is
Each of the consultants is
Either of the answers is correct

However, there are 5 exceptions: what we call the SANAM pronouns: Some, Any, None, All, More/Most. These can be either singular or plural, depending on the object of the preposition. Both of the following are correct:

Most of the money was stolen.
Most of the items were stolen.

In your example sentence:
Most of the purported health benefits of tea comes from antioxidants-compounds also found in beta carotene, vitamin E, and vitamin C that inhibit the formation of plaque along the body’s blood vessels.

The subject should be "health benefits" rather than "most." We need the plural verb: "come." (Remember that plural verbs don't have an 's' but singular verbs do).

If the OA given for this problem indicates otherwise, it is incorrect.