Where can the lines containing the altitudes of an obtuse triangle intersect?

Choice C) III only

As shown in the attached image, the altitudes are lines that are perpendicular to the sides of the triangle and they go through the opposite vertex. In the example shown, the orthocenter is the result of intersecting the altitudes. The orthocenter is outside the obtuse triangle. It will never be on the triangle or on the inside of the triangle.