Answer:- C. It is a closed figure.
E. All of its angles have equal measures.
F. Its sides are congruent line segments.
Explanation:-
A. False.
Reason:-Quadrilateral is a type of polygon.
B. False.
Reason:-Equilateral triangle is a regular polygon with interior angles measure 60°.
C.True.
Reason:- Definition of regular polygon.
D.False.
Reason:-Hexagon is a type of regular polygon with 6 sides .
E.True.
Reason:- Property of regular polygon.
F.True.
Reason:- Property of regular polygon.