Explanation on how answer could be option C
$v_7$ is the last node that should be pushed on the stack.
But there is a possibility that there exists some code which does not push the last node on the stack,
for doing such a thing it is required, say, to maintain a counter for number of nodes being pushed to the stack. Its good to maintain such a counter, this saves us from unnecessary push and checks for visited marked nodes, once nodes except one are already traversed.
$v7$ turns out to be the last node.
Hence, answer = option C
