Which sentence has an incorrect subject-verb agreement?

The sentence "Across the bay, fleets of old fishing boats was seen on the horizon" contains an incorrect subject-verb agreement because the subject "fleets" is plural, while the verb "was" is singular. In English, subjects and verbs must agree in number; therefore, the correct verb form should be "were" to match the plural subject "fleets." This means the correct sentence should read, "Across the bay, fleets of old fishing boats were seen on the horizon."

The other sentences correctly maintain subject-verb agreement. In the second option, the subject "many of the people" aligns with the verb "seems" in context, even though its grammatical form appears incorrect due to an issue with the verb form reflecting plurality. The third option, with "psychologists" as the plural subject and "have" as the plural verb, is consistent, as is the fourth sentence where "I’m serving barbecue" appropriately links with the singular subject.