8. Given four distinct lines on a plane, let the number of intersection points of two or more lines be $n$. Then the sum of all $n$ is ( ).
(A) 14
(B) 16
(C) 18
(D) 19
(E) 21
8. D.

Obviously, the possible number of intersection points of four lines is $0, 1, 3, 4, 5, 6$. Therefore, the sum of all possible values of $n$ is 19.