Answer:
D.
Step-by-step explanation:
You could find out if the seatbelt unlatched by learning the trajectory at which the girl was hurt/ launched out of the car. They would then compare that set of data to what would've happened if the seatbelt hadn't unlatched.
Hope this helps. I don't know much about law but this was kinda common sense to me having been using my math and science brain.