A Researcher Has Divided His Research Subjects into Two Groups

A researcher has divided his research subjects into two groups. For one group, the CS is 10 seconds long and signals a brief US at the end of the procedure. The time between trials is 30 seconds. In another group, the CS is 2 seconds long with a brief US at its end, and the time between trials is 6 seconds. You expect the

A) second group to condition more rapidly because the intervals between trials are shorter.
B) first group to condition more rapidly because the intervals between trials are longer.
C) two groups to condition at more or less the same pace.
D) second group to condition more rapidly because it is exposed to a longer interstimulus interval.