Propellant tanks containing oxygen and nitrogen tetroxide can be pressurized using _________

A)
helium alone
B)
nitrogen alone
C)
nitrogen and helium respectively
D)
helium and nitrogen respectively

Correct Answer :   helium alone


Explanation : Nitrogen will react with oxygen and nitrogen tetroxide and decrease the density and concentration of the oxidizer. In order to avoid that, helium is used instead of nitrogen for pressurizing the tanks containing oxygen or nitrogen tetroxide.