In Order to Investigate Whether Talking on Cell Phones Is

In order to investigate whether talking on cell phones is more distracting than listening to car radios while driving, sixty-four student volunteers (from a single college class) were randomly assigned to a cell phone group or a radio group (32 students were assigned to each group) . Each student "drove" a machine that simulated driving situations. While "driving" the simulator, a target would flash red at irregular intervals. Participants were instructed to press the "brake" button as soon as possible when they detected a red light. Participant response times were measured as the time between the red light appearing and pushing the brake button. While driving, the radio group listened to a radio broadcast and the cell phone group carried on a conversation on the cell phone with someone in the next room.
The cell phone group had an average response time of 585.2 milliseconds (SD = 89.6) , and the control group had an average response time of 533.7 milliseconds (SD = 65.3) .
-Describe the parameter of interest in words.

A) Mean response time under simulated driving situations.
B) Difference in long-run mean response time between drivers talking on cell phones and drivers who listen to a radio broadcast.
C) Difference in long-run proportion of response times between drivers talking on cell phones and drivers who listen to a radio broadcast.
D) Difference in sample mean response time between drivers talking on cell phones and drivers who listen to a radio broadcast.