Answer:
(a) A radius of the circle can be named as QR.
(b) A diameter of the circle can be named as RS, as it passes through the center Q.
(c) A chord of the circle can be named as QS, as it's a line segment that joins two points on the circle.
(d) If the length of QT is 7 units, and QR is a radius of the circle, then the length of RS is also 7 units because RS is a diameter of the circle, and a diameter is twice the length of a radius.