Answer:
The correct answer option is 'orthocenter'.
Explanation:
The point of concurrency of the altitudes of a triangle is called the 'orthocenter'.
Orthocenter is the point in a triangle where all of the three altitudes of the triangle intersect each other.
Explaining further, a line which is perpendicular to the opposite side and passes from a vertex of a triangle is called the altitude of the triangle.
Therefore, the correct option is D. orthocenter.