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:
Air quality is a measure of pollutants in the air.
answer:
Air quality is a measure of what in the air?


question:
Distance over time in a given direction determines velocity.
answer:

What determines velocity?