Question

parallel lines
lines that intersect to form a right angle.
two lines in the same plane that do not intersect.
two angles that add up to 90 degrees
two angles whose sizes add up to 180 degrees

Explanation:

Parallel lines are defined as two lines in the same plane that do not intersect. The other descriptions refer to perpendicular lines (lines that intersect to form a right - angle), complementary angles (two angles that add up to 90 degrees), and supplementary angles (two angles whose sizes add up to 180 degrees).

Answer:

Two lines in the same plane that do not intersect.