Question

which diagram represents the theorem that the altitudes of a triangle intersect at a point?

Explanation:

An altitude of a triangle is a perpendicular segment from a vertex to the line containing the opposite side. The theorem states that the altitudes of a triangle intersect at a point (the orthocenter). We need to look for a diagram where three lines (each representing an altitude - perpendicular from a vertex to the opposite side) meet at a single point.

Answer:

The first diagram (assuming the first one in the order presented in the problem - the one with three lines drawn as altitudes intersecting at a point inside the triangle).