Question

why can't a line segment have 2 midpoints????????????????????????????????????????

Answer 1

A midpoint is the point in the middle.

Obviously, a line cannot have two points in the middle.

Answer 2

think of the midpoint of a line as being the half-point of a line

there can only be one point that divides this line into 2 equal parts

A--------MP--------B

A--------C--------B

C is the midpoint of line AB

now, you could find the midpoint of
segment AC

A----MP----C--------B
A-----D----C--------B

so, C is the midpoint of line AB
and D is the midpoint of segment AC

I think you are thinking that since line AB has midpoints D and C, therefore, more than 1 midpoint

but remember,
D is the midpoint of segment AC
C is the midpoint of line AB

hope this helps