Two lines that are both perpendicular to the same line are what relative to each other?

• A. Parallel
• B. Perpendicular
• C. Intersecting
• D. Similar

Answer: (A)

Two lines that are perpendicular to the same line are parallel to each other in the same plane. Since each of them forms a right angle with the common line, they point in the same direction and never cross. Picture a vertical line with two horizontal lines crossing it; those horizontals run side by side and do not meet. In standard plane geometry, that makes them parallel (they could be distinct lines or the same line).