Select the answer that shows the definition of a right angle.
Choice 'A' an angle, formed by two opposite lines, that measures exactly 90°
Choice 'B' an angle, formed by two intersecting lines, that measures exactly 90°
Choice 'C' an angle, formed by two opposite lines, that measures exactly 180°
Choice 'D' an angle, formed by two intersecting lines, that measures exactly 180°
