Final answer:
The sentence with the correct subject-verb agreement is "Tommy and Julia have not finished their project" as the subject is plural and matches the plural verb 'have'.
Step-by-step explanation:
The sentence with the correct subject-verb agreement is "Tommy and Julia have not finished their project." In this sentence, the compound subject Tommy and Julia is plural, and therefore, the verb must also be plural (have). The other sentences do not exhibit correct subject-verb agreement. For instance, "Maria and George is not coming to the party" should use "are" instead of "is" because Maria and George form a plural subject. Likewise, "My new puppy do not come when I call her" should use the singular verb "does" instead of "do" because the subject new puppy is singular. Lastly, "None of the birds on the beach were seagulls" is correct if 'none' is considered singular; however, it can be deemed correct or incorrect depending on whether 'none' is treated as singular or plural, as it can be both. But based on traditional rules, it is commonly treated as singular when it means 'not one'.