Final answer:
The correct biconditional statement for collinear points is 'points are collinear if and only if they lie on the same line.'
Step-by-step explanation:
The statement "Points that lie on the same line are collinear." written as a biconditional statement is: A. points are collinear if and only if they lie on the same line. A biconditional statement expresses that two conditions are both necessary and sufficient for each other. In this case, being on the same line is necessary and sufficient for points to be collinear, and vice versa. The other options listed represent only one direction of the biconditional relationship or do not use the phrase 'if and only if', which is essential for expressing a biconditional.