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

[Q]: Amount of salt are aquatic biomes often classified.
[A]: How are aquatic biomes often classified?


[Q]: Learned behavior is adaptive because they are flexible, capable of changing if the environment changes.
[A]: What kind of behaviors are adaptive because they are flexible, capable of changing if the environment changes?


[Q]: Mucosal tissues are major barriers to the entry of pathogens into the body.
[A]:
What type of tissues are major barriers to the entry of pathogens into the body?