The determiners are underlined,so please check it carefully.
You have underlined only the articles (a, an, the) which are a part of determiners.
There are many other determiners: each, any, some, many, few, a few, this, that, these, those, my, his, her, your, our, their, its, a lot of, most, numbers (like ten , twenty, one, etc.), first, a little, etc.
There are many other determiners: each, any, some, many, few, a few, this, that, these, those, my, his, her, your, our, their, its, a lot of, most, numbers (like ten , twenty, one, etc.), first, a little, etc.