What are the main elements of a circumference?

The radius is the segment that connects the center point to any point on the circumference.
The diameter is the segment that connects two points on the circumference, passing through the center point.
The chord is a line that connects two points on the circumference.
The arc is a part or subset of the circumference, limited by two points on it.
a) Statements I, II, and III are correct.
b) Statements I, II, and IV are correct.
c) Statements I, III, and IV are correct.
d) Statements II, III, and IV are correct.