instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
People stopped adding lead to gasoline because of environmental pollution.
answer:
Why did people stop adding lead to gasoline?

question:
Pyramid ecosystem is used to show energy flow through the trophic levels.
answer:
What is used to show energy flow through the trophic levels?

question:
There are three chambers in a reptiles heart.
answer:
How many chambers are in a reptiles heart?