The internal energy of a material is determined by
its temperature
the kinetic energy of its molecules
the potential energy of its molecules
the combined amount of kinetic and potential energy of its molecules

i believe i could be wrong but i think its kinetic energy.

its the combined amount of kinetic and energy molecules. if wrong then temperature for backup

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

hope this ! : )

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.