Final answer:
The biconditional statement is 'Points are collinear if and only if they lie on the same line', which expresses that the concepts of being collinear and lying on the same line are mutually inclusive and necessary conditions of each other.
Step-by-step explanation:
The question asks for the statement that is written as a biconditional statement. A biconditional statement in mathematics is one where two statements are both necessary and sufficient conditions for each other. The biconditional statement is commonly identified by the phrase 'if and only if', which indicates the mutual relationship between them. In this context, when talking about collinear points, the biconditional statement is: 'Points are collinear if and only if they lie on the same line'. This statement shows that the condition of points being collinear is both necessary and sufficient for them to lie on the same line, and vice versa.