Two lines are parallel. Which statement is true?

• A. They have the same slope.
• B. They have the same x-intercept.
• C. Their slopes are negatives of each other.
• D. They must share exactly one point.

Answer: (A)

Parallel lines go in the same direction, so the rate at which y changes with x is the same for both. That means their slopes are equal. If you write each line as y = m x + b, parallel lines share the same m but have different b’s, so they rise or fall at the same rate but start from different positions, never crossing each other.

The other statements don’t fit: parallel lines do not share a single x-intercept because they never meet; having slopes that are negatives of each other describes perpendicular lines, not parallel ones; and parallel lines do not intersect at exactly one point—their intersections are either none (distinct parallel lines) or infinitely many points (if the lines are the same). (If both lines are vertical, their slope is undefined, but they’re still parallel in direction.)