Stacks are used where there is a long expression to be evaluated which is having many brackets to guide us so that which operations need to carried out first.

Now stacks work according to last In first out concept that is The elements which are at the end of the stack can be popped out, For example, consider a stack of books You can only remove a book which is at the top.

This concept is employed in Bracket matching, where opening brackets are pushed In into the stack and closing brackets are popped out, if after all the brackets are covered and if we find our stack to be empty we say that bracket matching is successful.

Therefore the answer to Your Problem is C.