In an Experiment, Pigeons Were Given the Opportunity to Press

In an experiment, pigeons were given the opportunity to press one button that would immediately give 2 seconds of access to a grain hopper or another button that would provide 4 seconds of access after a 4-second delay. The result was that almost all of the pigeons

A) alternated between the two keys.
B) chose the key that gave immediate access.
C) chose the key that gave more access after a delay.
D) learned to press both buttons simultaneously.