A car manufacturer created a new voice-control system that allows drivers to have limited use of their phones while keeping both hands on the wheel. They want to know if the system results in drivers making fewer mistakes, so they recruit volunteers for an experiment. Each subject is randomly assigned to one of three groups: voice-controlled phone use, regular phone use, or no phone use at all. Subjects drive the same simulated course while researchers send notifications at set moments to the drivers who can use phones. The researchers will then compare how many mistakes are made between the groups. What is the purpose of the experiment, and how are the subjects divided into groups? a) The purpose is to test the effectiveness of a new voice-control system. Subjects are divided into three groups: voice-controlled phone use, regular phone use, or no phone use at all. b) The purpose is to study driver behavior. Subjects are divided into two groups: voice-controlled phone use and regular phone use. c) The purpose is to analyze phone-related mistakes. Subjects are divided into two groups: voice-controlled phone use and no phone use at all. d) The purpose is to test the impact of phone use on driving. Subjects are divided into three groups: voice-controlled phone use, regular phone use, or no phone use at all.