Official Explanation
The underlined portion contains no errors. The was is correctly used since Everyone is always considered to be singular. Everyone is an indefinite pronoun, of which there are three types. The pronouns of the first type are always singular: everyone, each, either, neither, someone, somebody, nobody, anyone, anybody, everybody, one, and no one.
Those of the second type are always plural: both, few, many, and several. Those of the third type may be singular or plural, depending on whether the noun to which they refer is singular or plural: some, more, most, and all (“some of the cake [singular] is . . .”; “some of the boys [plural] are . . .”).
In choice (C), I should be me because it is the object of except.
Choices (D) and (E) are both incorrect because accept is a verb, not a preposition (an error of diction).
The correct answer is (A).
Hope it helps