one
A line that is perpendicular to the segment of a plane and passes through the midpoint.
3
equilateral triangle
Angle bisectors intersect at the incenter which is equidistant from the sides
1
2
All bisectors intersect the line segment at the midpoint. There can be multiple bisectors, intersecting at the midpoint at different angles, but they all intersect the line segment at its midpoint. The midpoint separates the line segment into two equal halves.
Only one.
one
Explain why a line segment can have one midpoint but many bisectors
Exactly one. No more, no less.
no-- It only has one. Since it is a segment, it has a definite start and end, so it has only one middle (the bisector).
Since there is no such word as "perpindicuar", it is difficult to be sure. A line segment can have only one perpendicular bisector.
Infinitely many. Each line segment contains one point which bisects it. Any one of the infinite lines through that point, apart from the original line, is a bisector.
A line that is perpendicular to the segment of a plane and passes through the midpoint.
Equilateral triangles have 3 perpendicular bisectors