Regarding Random-Dot Stereograms

Multiple Choice

Regarding random-dot stereograms,

A) you can usually tell from either half alone which part of the stereogram will appear in depth when the two halves are viewed together
B) if low spatial frequencies are removed from one half and high spatial frequencies from the other half, stereopsis disappears.
C) if the same spatial frequencies are removed from both halves, stereopsis disappears.
D) all of these