Final answer:
Drivers under age 20 are prohibited from using their cellphone while driving except in the case of an emergency.
Step-by-step explanation:
In most states in the United States, drivers under age 20 are indeed prohibited from using their cellphone while driving, except in the case of an emergency. This rule is in place because young drivers are more likely to be distracted while using their phones, which can increase the risk of accidents. Penalties for violating this law vary by state, but they often include fines and license suspensions.