Answer with explanation:
Postulates or Axioms are universal truth statement , whereas theorem requires proof.
Out of four options given ,the following are basic postulates of euclidean geometry:
Option C: A straight line segment can be drawn between any two points.
→To draw a straight line segment either in space or in two dimensional plane you need only two points to determine a unique line segment.
Option D: any straight line segment can be extended indefinitely
→Yes ,a line segment has two end points, and you can extend it from any side to obtain a line or new line segment.
We need other geometrical instruments , apart from straightedge and compass to create any figure like, Protractor, Set Squares.
So, Option A is not Euclid Statement.
Option B , is a theorem,which is the angles of a triangle always add up to 180 degrees,not a Euclid axiom.
→Option C, and Option D