Quiz: Two-BFS Method

Two-BFS diameter algorithm: BFS from any node $a$, find farthest node $b$, BFS from $b$, find farthest node $c$. Distance $b$ to $c$ is the diameter. Why does this work?

1. A.It only works for binary trees
2. B.BFS always finds diameter endpoints
3. C.You need three BFS calls, not two
4. D.The farthest node from any node must be a diameter endpoint