9. A bench can accommodate exactly 7 adults or 11 children. When $N$ benches are connected end-to-end, the same number of adults and children sit together, filling the benches exactly. Then the smallest possible value of the positive integer $N$ is ( ).
(A) 9
(B) 18
(C) 27
(D) 36
(E) 77
9. B.

Notice that, $(7,11)=1,[7,11]=77$.
Therefore, there are 77 adults and 77 children sitting on $N$ benches.
Thus, $N=\frac{77}{7}+\frac{77}{11}=18$.