In which situation is it illegal to use your cellphone while driving?

Answer: B — When you are holding the device without a hands-free feature

Using a cellphone while holding the device without a hands-free feature is illegal because it poses a significant risk to safe driving. When a driver holds a cellphone, their attention is divided between the phone and the road, impairing their ability to react to sudden changes in traffic or road conditions. This law is in place to minimize distractions that can lead to accidents. While using a hands-free device is typically permitted, the other options reflect scenarios where the use of a cellphone is either allowed or doesn't pose the same level of distraction. For example, being stopped at a signal or driving at low speeds might lead some to believe it's safer to use a phone; however, these situations still carry risks and are not outright prohibited in the same manner as holding the device. Therefore, the prohibition against holding the phone emphasizes the importance of maintaining full attention on the driving task.