Option A – Parallel.
Since a tangent is perpendicular to the radius at the point of contact, both tangents at the ends of a diameter are perpendicular to the same diameter, making them parallel to each other.
Theorem 10.1 states tangent ⊥ radius at point of contact. The two tangents at the extremities of a diameter are both perpendicular to the same line (the diameter), so by geometry they must be parallel. Exercise 10.2, Q.4 directly asks students to prove this. Examiners expect option A with a one-line justification.