Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Sporopollenin protects the pollen of seed plants and spores of seedless plants.
What protects the pollen of seed plants and spores of seedless plants?

Light retains its original color under water because frequency remains the same when light is refracted.
Light retains its original color under water because what remains the same when light is refracted?

Mars is the fourth planet from the sun.
Which is the fourth planet from the sun?