1. C. Are because the subject in the question is 'those loud teenagers" which is plural.
2. D. The sentence might contain two subjects but the verb will take the form of the subject closest to it (one of his colleagues).
3. D. Mops: because whenever two subjects are joined by "or" or "nor", the verb should agree with the subject closest to it (dishwasher), which is singular.
4. B. is not: When the adjective "enough" is used to modify a plural subject (peaches), the subject requires a verb in a singular form.
