The verb should agree with the subject – not necessarily the noun that appears just before the verb.
Sometimes another noun will come between the subject and the verb, but only the subject should determine the number of the verb. Here are some sentences that get this right:
The monkey, as well as the chimpanzees, enjoys eating bananas.
“Chimpanzees” is obviously plural, but because it’s set aside by “as well as,” it’s not part of the subject. (In addition to, along with, and similar phrases work the same way as as well as.) The subject is “monkey” and “monkey” is singular, so the verb is singular, too.
The point of the activities was to learn more about primates.
Again, a plural noun (“activities”) appears closer to the verb (“was”), but the subject (“point”) is singular. Therefore, the verb is singular.
When a compound subject is linked by “or” or “nor,” the verb should agree with the subject that’s closer to the verb.
Again, here are some proper sentences:
Either the baby or the parents want a nap.
Either the parents or the baby wants a nap.
These sentences are virtually identical. However, in the first case, the plural noun (“parents”) of the compound subject is closer to the verb, so the verb is plural (“want”), while in the second the singular noun (“baby”) of the subject is closer, so the verb is singular (“wants”).
Quantities sometimes call for a singular verb.
This one is really tricky, so let’s start with a simple example.
Seventeen pancakes are covered in maple syrup.
“Pancakes” is plural, and so is “are,” so everything’s fine here. Now look at this example:
Seventeen pancakes is too much for one meal.
Perhaps surprisingly, this sentence is also right! That’s because this sentence is discussing “seventeen pancakes” as a quantity. The first example was discussing seventeen particular pancakes, but this one is talking about a number of pancakes, so the verb should be singular.
This rule usually also applies to standardized units of measurement. If you are referring to multiple specific pounds or minutes, for instance, you should use a plural verb:
The last five pounds are often the hardest to lose.
The first ten minutes were the most exciting part of the game.
However, if you are using the number of minutes or pounds to express a general quantity, you should use a singular verb:
Five pounds is too much for someone to lift immediately after this surgery.
Ten minutes is more than enough time to change your shoes.
Knowing these guidelines is bound to help you polish your subject-verb agreement and writing, so keep them in mind!