AFFIRMATIVE
There isn't any / some / a food in my bag.
There isn't ANY in my bag.
There is / There are / Is there some rulers in the classroom.
There are some rulers in the classroom.
Is there / Are there / There are any blue pens in the shop?
Are there any blue pens in the shop?
There are any / some / a exercises in the textbook.
There are some exercises in the textbook.
Is there / Are there / There is a ruler on your desk?
Is there a ruler on your desk?