___________ are used for preventing the propellant flow back into the tanks and avoiding inadvertent mixing of propellants in the flow passage.

A)
Filters
B)
Check valves
C)
Drainage valves
D)
Isolation valves

Correct Answer :   Check valves


Explanation : Check valves allow flow to pass only in one direction. Using them will prevent the flow from going back to the tank or inadvertent mixing.