Which of the followings are true for a complete binary tree?
A. It has always odd number of vertices.
B. With i internal vertices, it has i + 1 leaves.
C. With ℓ leaves it has ℓ - 1 vertices.
D. With 2n - 1 vertices, it has n leaves.
Choose the correct answer from the options given below:

Correct option is B

To determine which statements are true for a complete binary tree, let us consider each statement:
A. It has always an odd number of vertices: A complete binary tree does not necessarily have an odd number of vertices. The number of vertices in a complete binary tree can be any number, depending on the number of levels it has. Therefore, this statement is false.