Question

By determining if the subject is singular or plural, what can be determined about the verb?

Answer 1

The verb agreement. Here's a basic sentence to help explain:

The boy is/are happy.
The boys is/are happy.

In the first example, the verb "is" matches the singular boy. In the second, "are" is the correct choice. Here's another.

The boy help/helps himself to another cookie.
The boys help/helps themselves to another cookie.

With some verbs, it's almost as easy as moving the "s." If there is an "s" on the subject, then there isn't one on the verb. If there isn't on on the subject, then there is on on the verb. Of course that doesn't work with the is/are example, but the principle is the same.