If node A has three siblings and B is parent of A, what is the degree of A?

The degree of a node in a tree is the number of children that node has. This is a property of the node’s own descendants — it does not depend on the node’s siblings (the other children of the same parent) or on the node’s parent.

Here, A has three siblings and B is A’s parent. This tells us that B (A’s parent) has four children in total — A plus its three siblings — so B’s own degree is 4. However, the problem gives no information at all about how many children A itself has: A could be a leaf with 0 children, or could have any number of children.

• 0 would only follow if the problem stated that A is a leaf node — it does not.

• 3 is the number of A’s siblings, not the number of A’s children.

• 4 is the number of children of A’s parent B (A plus its three siblings), not the number of A’s own children.

Since A’s own child count is never stated, none of 0, 3, or 4 can be justified as the degree of A from the given information — the degree of A cannot be determined, so the correct response is “None of the above.”