Rule 1:
In Singular Subject must use these verbs is, was, has, does, or verb ending with s or es but these verb are of singular forms of verbs. Example:
a) The boy carries a pile of books everyday.
b) Rita is writing a book for her assignment

Rule 2:
In Plural Subject must use these verbs are were, have, do or verbs without s or es because these are the plural forms of verbs.xample:
a) The boys carry a pile of books everyday.
The students are writing a book for their assignment

Rule 3:
If there is pronoun YOU as the sentence subject, we MUST use the plural form of verbs, which are as follows:- are, were, have, do or verbs without s or es ending. Example:
a) You are responsible for all the activities in the classroom
b) You have to give me the book that you borrowed yesterday