Consider these functions:push() : push an element into the stackpop() : pop the top-of-the-stack elementtop() : returns the item stored in top-of-the-stack-nodeWhat will be the output after performing these sequence of operationspush(20);push(4);top();pop();pop();pop();push(5);top();

• A. 20
• B. 4
• C. stack underflow
• D. 5