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) .
-In terms of investigating whether talking on cell phones is more distracting than listening to car radios while driving, which of the following is the correct null hypothesis?

A) There is an association between whether one talks on a cell phone or listens to the radio while driving and response time.
B) There is no association between whether one talks on a cell phone or listens to the radio while driving and response time.
C) Talking on a cell phone increases your response time compared to listening to the radio.
D) Talking on a cell phone does not increase your response time compared to listening to the radio.