Given a fact, create a question that can be answered using the fact. Construct the question such that it is unambiguous, has a unique answer and the answer can be given using the fact.

Fact: In the photosynthesis process oxygen has the role of waste product
Unlike CO2, oxygen is a waste product of?

Fact: a source of something supplies that something
a retailer gets an order of aluminum delivered weekly. Where is the aluminum likely coming from?

Fact: An example of replacing a natural resource is planting new trees where a forest once stood
If a person restores a garden complete with oaks, then they have replaced?