The correct answer is is. This question tests your knowledge of subject-verb agreement, specifically with indefinite pronouns and phrases like "one of the." In the sentence "One of the books __________ missing," the true subject of the verb is "One," not "books." "Of the books" is a prepositional phrase modifying "One," indicating which specific "one" we are talking about. The prepositional phrase does not affect the number (singular or plural) of the subject.
Since "One" is a singular pronoun, the verb must also be singular. Therefore, "is" is the correct choice for a singular subject in the present tense.
- Are: This is a plural verb and would be incorrect because the subject "One" is singular.
- Were: This is a plural past tense verb and is incorrect for the same reason as "are," and also because the sentence implies a present state.
- Have: This is a plural verb (or used with plural subjects in present perfect tense) and is incorrect because the subject "One" is singular.
Remember that when you have a phrase like "one of the [plural noun]," the verb always agrees with "one," which is singular. This is a common point of confusion in English grammar, but understanding the true subject clarifies the choice.