What speeds must be disabled in a mixed 802.11 b/g WLAN to allow only 802.11 g clients to connect?

What speeds must be disabled in a mixed 802.11 b/g WLAN to allow only 802.11 g clients to connect?

A.
6,9,12,18

B.
1,2,5.5,6

C.
5.5,6,9,11

D.
1,2,5.5,11