Which of the following best completes this definition? Two lines are parallel if and only if ______________. A. they intersect and form acute angles B. they do not lie in the same plane and do not intersect C. they intersect and form right angles D. they lie in the same plane and do not intersect

Answer 1

The best completion for the definition is: D. they lie in the same plane and do not intersect.

This definition captures the essential property of parallel lines in Euclidean geometry.