You are told that p(a | b) = p(b | a). which statement below must be true?
a and b are equally likely
p(a | b) = 0.5
a and b are independent
a and b are dependent

The best answer to the question that is being stated above would be that A and B are both dependent. If I was told that P(A | B) = P (B | A), then the true statement is that both variables inside would be dependent upon each other, no matter if you exchange their places with one another.