Awareness of the CS-US Contingency Appears to Be _____ for a Response

Multiple Choice

Awareness of the CS-US contingency appears to be _____ for a response to be acquired when the:

A) crucial; CS precedes and overlaps the US.
B) crucial; CS and the US are separated by a brief delay.
C) unnecessary; US precedes the presentation of the CS.
D) unnecessary; CS and US are in different sensory domains.