The five items P,Q,R,S and T are pushed in a stack, one after the other starting from P. The stack is popped four times and each element is inserted in a queue. Then two elements are deleted from the queue and pushed back on the stack. now one item is popped from the stack. The popped item is:

Concept:Stack:Stack is a linear data structure that allows to insert or delete elements from one end i.e. from the top of the stack. It follows a particular order in which elements are INSERTED or deleted i.e. LIFO (Last in first out).Queue:Queue is a linear data structure in which elements are inserted from one end and deleted from the other ends. It follows FIFO PROPERTY i.e. first in first out.Explanation:Given FIVE items P, Q, R, S, and T.These are pushed into the stack as : T (TOP)SRQPNow stack is popped four TIMES, each item popped is inserted into queue.So, items that are popped from the stack are: T, S, R, QAfter insertion into queue , queue looks like :QRST (FRONT)Now, two items are deleted from the queue which are: T, SThese are inserted back into the stack.Stack will be :S (TOP)TPQueue will be :QRNow, one item is popped from the stack which is S.