Final answer:
Vehicles must stop moving and become stationary on a two-lane highway when a school bus is loading children to ensure their safety.
Step-by-step explanation:
The question you've asked pertains to traffic regulations and safety, specifically concerning the necessary actions when encountering a school bus loading children on a two-lane highway. When traveling in the opposite direction on a two-lane highway, vehicles are required to stop moving and become stationary while a school bus is loading or unloading children.
This rule is crucial to ensuring the safety of children who may be crossing the road, and it is legally enforced in many regions. Ignoring this safety precaution could lead to severe consequences, including legal penalties and endangering the lives of young students.