I need help with this. Please

Consider the relations R(A,B) and S(A,B), where R has a foreign key referencing Svia B, and S has a foreign key referencing R via A. Which of the following is guaranteed to produce fewer than, or at most the same, number of tuples as any of the others? Select one: a. RUS b. RTB (S) c. There is not enough information to answer this. d. RS e. TA (R) AS