Quiz: Ancestor Check

You want to check if node $a$ is an ancestor of node $b$ in $O(1)$ time. You have tin and tout arrays. Which condition do you check?

1. A.tin[a] < tin[b]
2. B.tin[a] <= tin[b] and tout[b] <= tout[a]
3. C.tout[a] < tout[b]
4. D.tin[a] == tin[b] - 1