Positive statements in economics are statements that intend to describe how things are and how things actually work. That is, positive statements are objective statements that can be tested, amended, or rejected by referring to the available evidence. On the other hand, a normative statement is a prescriptive statement, like the ones expected to be made by a policy adviser, involving normative judgements and prescriptions about how the world should be. The statement in the question is about a common belief about the tradeoff between inflation and unemployment, which is popular among economists. The correct answer is A.