Mandatory motor vehicle liability proof must be:

The correct answer highlights that mandatory motor vehicle liability proof must be in effect in the vehicle being operated. This means that when you are driving, your insurance should be current and valid for the vehicle you are using at that time. Carrying proof of insurance ensures that you can demonstrate that you meet the state’s requirements for financial responsibility in case of an accident.

Having liability coverage that is "in effect" not only protects you legally but also provides financial coverage for damages or injuries you may cause while driving. This legal requirement emphasizes the importance of being responsible and prepared while on the road.

The other choices reflect common misconceptions about the requirements for insurance proof. It's not sufficient for the proof to merely be displayed at all times or stored in the glove compartment; rather, it must be actively valid when the vehicle is in operation. Similarly, insurance cannot be required only during inspections; it is an ongoing requirement when you are driving. Hence, the focus is on ensuring that active coverage is in place whenever you are handling a vehicle.