Answer:
Underground!
Step-by-step explanation:
In a car: A car is not a safe place to be during a tornado. Tornadoes can easily lift and toss vehicles, making this a very dangerous choice.
Lying on the ground: This is also not a safe option because flying objects around you could bump towards you and get hurt or worse.
Underground similar to basement: This is the safest option. Tornado shelters or basements provide the most protection from the tornado's destructive forces.
In a bathroom: If you don't have an underground, go into a bathroom. It's much safer than the other two questions.
I hope this helps. :D