TASK DEFINITION: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
PROBLEM: Amount of salt are aquatic biomes often classified.

SOLUTION: How are aquatic biomes often classified?

PROBLEM: Elements are pure substances that make up all matter.

SOLUTION: Elements are pure substances that make up what?

PROBLEM: Amphibians sexually reproduce through external or internal fertilization.

SOLUTION:
Through what method or methods of fertilization do amphibians sexually reproduce?