According to the Rescorla-Wagner Model's Explanation of Blocking

According to the Rescorla-Wagner model's explanation of blocking,

A) some excitatory conditioning occurs on the first compound conditioning trial, but after that trial the added element develops inhibitory associative strength.
B) some excitatory conditioning occurs on the first compound conditioning trial, but after that trial no further associative strength accrues to the added element.
C) very little conditioning occurs on the first or any subsequent trials, as the US cannot support any more associative strength to be gained by either stimulus in the compound.
D) inhibitory conditioning begins to occur to the added element on the first compound conditioning trial and continues to accrue, in turn preventing any excitatory associative strength from accruing to the compound.