8.30 people attend a certain gathering, among them, 20 people know each other, and another 10 people do not know anyone else. People who know each other greet with a hug, while those who do not know each other greet with a handshake. Then, the total number of handshakes at this gathering is ( ).
(A) 240
(B) 245
(C) 290
(D) 480
(E) 490
8. B.
$$
C_{30}^{2}-C_{20}^{2}=245 .
$$