Topic: Subject Verb Agreement,

Best Answer Explained in Below-:

The sentence 'Everybody who — a fever must go home immediately' requires a verb that correctly matches the subject "everybody." In English grammar, "everybody" is treated as a singular noun. Therefore, any accompanying verb must also be in the singular form.

Looking at the provided options:

A) "have" is a plural verb and does not agree with the singular subject "everybody."
B) "had" is also a past tense verb, which does not fit the context, as we are discussing a current situation—those who currently have a fever.
C) "has" is the correct singular present tense form of the verb "to have," aligning perfectly with the singular subject "everybody."

D) "none" is simply not applicable, as we do have a fitting option.

Thus, the complete sentence reads: 'Everybody who has a fever must go home immediately,' indicating the present requirement for those who are currently experiencing a fever to leave. In summary, 'has' is the only grammatically and contextually appropriate choice here.