What distinguishes a diameter from other chords in a circle?

A diameter is specifically defined as a chord that passes through the center of the circle. This unique characteristic sets it apart from other chords, as no other chord will intersect the center. While it is true that the diameter is also the longest chord in the circle (making option A true as well), the defining feature of a diameter is that it must traverse the center.

In addition, the other options offer characteristics that are not universally true for all diameters. For instance, not all chords are perpendicular to one another (which is implied by option C), and while a diameter connects points on the circumference, this is true for all chords (making option D less specific). Hence, the defining trait of a diameter remains its passage through the center, which is why this understanding is crucial for recognizing the role of diameters in circle geometry.