Decide whether each statement is true or false. If a statement is true, say which of Euclid's five postulates apply to it, then write the converse and contrapositive statements, and then decide which of these statements are true (it may help to rewrite the statements in "if-then" form). If it is false, give a counterexample or explain why.

a. A triangle can be drawn from any three points that are not on the same line.

b. A square can be drawn from any four points not on the same line.

c. When two lines intersect, the four angles they make add to 360 degrees.

d. There is only one parallel line to any given line.