Question

which important indoor safety measure should be taken during a thunderstorm?
lie on the floor.
cover your head.
go to the basement.
move away from windows.

Explanation:

During a thunderstorm, moving away from windows is an important indoor safety measure. Windows can shatter due to lightning - related pressure changes or flying debris. Lying on the floor is more relevant for earthquakes. Covering the head is a general safety action but not specifically for thunderstorm - related indoor safety. Going to the basement is more associated with tornado safety.

Answer:

Move away from windows.