Consider a binary tree $T$ in which every node has either zero or two children. Let $n>0$ be the number of nodes in $T$. Which ONE of the following is the number of nodes in $T$ that have exactly two children?

Suppose the values $10,-4,15,30,20,5,60,19$ are inserted in that order into an initially empty binary search tree. Let $T$ be the resulting binary search tree. The number of edges in the path from the node containing 19 to the root node of $T$ is ________ (Answer in integer)

Consider the following $B^{+}$tree with 5 nodes, in which a node can store at most 3 key values. The value 23 is now inserted in the $B^{+}$tree. Which of the following options(s) is/are CORRECT?

Which of the following statement(s) is/are TRUE for any binary search tree (BST) having $n$ distinct integers?