Answer:
(D) A is the correct answer.
Step-by-step explanation:
A vertex is commonly known as the intersection of two sides of a plane figure and also The point about which an angle is measured is called the angle's vertex, and any angle associated with a given vertex is called the vertex angle.
since, the angle 4 is associated with a given vertex A,
Thus, the vertex of the angle 4 is "A".
Hence, option D is correct.