ANSWER
The name of the segment inside the triangle is

Step-by-step explanation
The segment inside the large triangle is a line from one vertex of the large triangle that meets the the opposite side of the large triangle at right angle.
Any line from one vertex of a triangle that meets the side opposite to that vertex at right angle is referred to as the

of the triangle.
Sometimes the altitude may fall outside the triangle.
Therefore the correct answer is option 2.