In Each Trial of an Experiment,participants See a Warning Signal

Multiple Choice

In each trial of an experiment,participants see a warning signal and then,a half-second later,see a pair of letters.The participants press one button if the letters are the same (e.g. ,W W) and a different button if the letters are different (e.g. ,P X) .In 80% of the trials,the warning signal is identical to the letters that will be shown on that trial.Here are the warning signals and the test stimuli presented on Trial 97 of the procedure:
Group 1: warning signal = L;test pair = L L
Group 2: warning signal = U;test pair = L L
Group 3: warning signal = +;test pair = L L
In this setup we should expect the fastest responses from

A) Group 3 and the slowest responses from Group 2.
B) Group 1 and the slowest responses from Group 3.
C) Group 1 and the slowest responses from Group 2.
D) Group 1 and no difference between Groups 2 and 3.