Q32

Consider two relations $R_1(A,B)$ with the tuples $(1,5), (3,7)$ and $R_2(A,C) = (1,7),(4,9)$. Assume that $R(A,B,C)$ is the full natural outer join of $R_1$ and $R_2$. Consider the following tuples of the form $(A,B,C):$ $a = (1,5,null), b=(1,null,7), c=(3,null,9), d=(4,7,null), e=(1,5,7),$ $f=(3,7,null), g=(4,null,9).$ Which one of the following statements is correct?