Property of friend classes is not transitive. If class A is friend of class B, and B is friend of C, then A is never a friend of C unless expilictly declared so. Property of friendship is not corresponding / commutative. If A is a friend of B, then B is not a friend of A. Functions of class A can have access to private / protected data of B without becoming member functions of B, but the converse is not true. So opions (a) and (b) are wrong. It is not that class B cannot be a friend of any other class. It can have a friendship with A while continuing friendship with C. So option (c) is also not correct.
Hence, none of the statments are true. Answer is option (d).
