An interrogative sentence asks a question. Interrogative
sentences end with a question mark. For example:
Who stole the cookies from the
cookie jar?
Who let the dogs out?
Why are there so many dogs eating
cookies in my yard?
All of these examples are interrogative sentences. They ask
a question, and they end with a question mark.
Some people get confused about whether a statement about
a question is an interrogative sentence. It is not. These types of
sentences are indirect questions because they are statements about
questions and do not require any answers. Therefore, they are declarative
sentences. Consider the following examples:
He asked who stole the cookies from
the cookie jar.
They wanted to find out who let the
dogs out.
Jenna wondered why there were so
many dogs eating cookies in her yard.
Even though these examples have people asking questions in
them, they are not direct questions and therefore are just declarative
sentences.