Question

which is the best response? if two angles formed by two intersecting lines, then they are vertical angles. if two angles are vertical angles, then they are opposite angles formed by two intersecting lines. if two angles are opposite angles formed by two intersecting lines, then they are vertical angles. if two angles are not vertical angles, then they are not opposite angles formed by two intersecting lines.

Explanation:

A conditional statement has a hypothesis (the "if" part) and a conclusion (the "then" part). The contra - positive of a conditional statement "if p then q" is "if not q then not p". For the statement "If two angles are vertical angles, then they are opposite angles formed by two intersecting lines", the contra - positive is "If two angles are not opposite angles formed by two intersecting lines, then they are not vertical angles".

Answer:

If two angles are not opposite angles formed by two intersecting lines, then they are not vertical angles.