Counting the numbers

Why are most 802.11b access points configured to use channels 1, 6, or 11, but rarely the channels in-between?

A) The other channels are government-restricted

B) The other channels provide slower bandwidth

C) The other channels are reserved for VoIP communication

D) The other channel frequencies overlap each other

E) The only good shows are on channel 1, 6, and 11.