A Researcher Records Mean Response Time in Milliseconds for a Group

A researcher records mean response time in milliseconds for a group of participants who perform a Donders A task and a Donders C task under two conditions. In one condition, they do the reaction time tasks alone; in the other condition, they perform the two tasks while doing a secondary attentionally demanding task at the same time. Reaction times for the Donders A task are the same for both conditions of the experiment; however, reaction times for the Donders C task are longer when the secondary task is being performed. Using the subtractive method, these results suggest

A) the secondary task slowed down the baseline reaction of the participants.
B) the secondary task speeded up the baseline reaction of the participants.
C) the secondary task slowed down the identification time of the participants.
D) the secondary task slowed down the selection time of the participants.