Theorem: the segment joining the midpoints of two sides of a triangle is parallel to the third side and half its length.
a two column proof of the theorem is shown but the statement and reasons are not in correct order.

Reasons:
I) Segment DE is half the length of segment AC. By substitution

II) Segment DE is parallel to segment AC. Slopes of parallel lines are equal.

III) The coordinates of point D are (4, 5) and coordinates of point E are (5, 3) By the midpoint form