Final answer:
Every segment does indeed have a unique line that bisects it; this is known as the perpendicular bisector, which divides the segment into equal parts at a right angle. So, the correct answer is option a.
Step-by-step explanation:
Every segment has a unique line that bisects it. The statement is True. In geometry, a line that bisects a segment is called a perpendicular bisector. This bisector is a line which cuts the segment into two equal parts at a 90-degree angle. Any given line segment has exactly one perpendicular bisector, thus making the initial statement true.
So, the correct answer is option a.