Indira are you referring to, during initial setup of an AdWords account?
Sometimes you have to select a broader category than you might like. And there are also some business categories, for various reasons that Google does not allow AdWords campaigns for.
If you tell us what type of business, we will provide helpful suggestions if possible. It would also be helpful to have a little more context about where you are at in the process of setting up your account, and what screen you are on.