When setting up a wireless network with multiple access points, why is it important to set each access point on a different channel?

When setting up a wireless network with multiple access points, why is it important to set each access point on a different channel?

A.
Multiple access points can be set up on the same channel without any issues

B.
Avoid over-saturation of wireless signals

C.
So that the access points will work on differentfreQuencies

D.
Avoid cross talk