21. Margo and her parents (visit-visits) each other offen 22. 6ther the cups or the glasses (are-as) in the dishwasher 23. Vem and Fred (need needs) a ride to work. 24. There (s-are) a dog, a cat, and a bird in the garage. 25. Neither Matt nor his brothers (was were) at the party. 26. Here into the main ring of the circus (come-comes) the trained elephants. 27. Bther the workers or the boss (deliver-delivers) the merchandise. 28. The committee (work-works) hard for better schools. 29. There (s-are) many things to do before the holidays. 30. The jury (was were) polled for their verdicts. 31. Here (is-are) the nails you need for the projects. 32. Either Joyce or Ellen (was-were) here. 33. The United States (is-are) a country of contrast. 34. A magazine and a book (was-were) lying on the floor. 35. The family (is-are) occupied with their individual problems.​

The corrections have been made based on the subject-verb agreement in English. <br /><br />Subject-verb agreement is a grammatical rule that states that the verb must agree with its subject in both number and tense. If the subject is singular, the verb must be singular; if the subject is plural, the verb must be plural.<br /><br />Here are how the sentences have been corrected based on the rules of subject-verb agreement:<br /><br />1. "Margo and her parents visit each other often": Here 'Margo and her parents' is plural, hence the verb 'visit' is used. <br /><br />2. "Either the cups or the glasses are in the dishwasher": We are talking about multiple items (cups or glasses) hence 'are' is used.<br /><br />3. In sentences 26 and 32, the rule applied is that with either/or or neither/nor sentences, the verb agrees with the nearer subject.<br /><br />4. In sentence 28, 'The committee works hard for better schools', the committee is treated as a single entity, hence the verb 'works' is used.<br /><br />5. In sentence 35, 'family' is considered a singular entity and hence 'is' is used. <br /><br />By adhering to the subject-verb agreement rule, the sentences have thereby been corrected.