They say we will not be able to afford to own houses in a few years

A. Reference

B. Case

C. Agreement

I’d say the answer is B, case

The statement "They say we will not be able to afford to own houses in a few years" is a Case. So the answer to your question would be letter B. This is just a case because it just describes the situation of the person and it is not an agreement nor reference because it does not any argument yet.