Given a statement, generate a question such that the answer is contained in that statement.

[EX Q]: Acid changes the shade of certain paper at different acidity.
[EX A]: What does acid change the shade of paper at?

[EX Q]: Octopuses use ink for hiding from sharks.
[EX A]: What do Octopuses use for hiding from sharks?

[EX Q]: Green plants are also known as producers
[EX A]:
What are green plants also known as?