instruction:
Given a statement, generate a question such that the answer is contained in that statement.
question:
Some species of lizards can go several weeks without eating.
answer:
How long can some lizards go without eating?

question:
Algae play significant roles in freshwater and marine environments.
answer:
Which species play significant roles in freshwater and marine environments?

question:
Broken bones heal when osteoclasts form new calcium structures.
answer:
What heals when osteoclasts form new calcium structures?