Choose the correct verb to complete the sentence: ‘Each one of us ____ a pen.’

This question tests subject-verb agreement, specifically with indefinite pronouns.

• 'Each one' is a singular indefinite pronoun. Even though 'us' is plural, the true subject of the verb is 'Each one', which always requires a singular verb.
• 'has' is the correct singular verb form for the third person singular, indicating possession. Therefore, "Each one of us has a pen" is grammatically correct.
• 'have' is a plural verb form and would be incorrect with a singular subject like 'Each one'.
• 'are' is a plural form of the verb 'to be' and is incorrect here, as the sentence requires a verb indicating possession, not a state of being.
• 'were' is the past tense plural form of the verb 'to be' and is incorrect for the same reasons as 'are', and also for tense if the context implies the present.