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

Q: Simple carbohydrates can be classified in terms of chain length.

A: Which carbohydrates can be classified in terms of chain length?
****
Q: Seismologists originally measured the intensity of an earthquake with the mercalli scale.

A: How did seismologists originally measure the intensity of an earthquake?
****
Q: Venom do puffer fish produce to protect itself.

A:
What do puffer fish produce to protect itself?
****