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.

[Q]: Fact: using a car causes pollution
[A]: Which form of travel causes the most pollution?


[Q]: Fact: water vapor condensing in clouds causes rain
[A]: Water vapor condensing in clouds may cause?


[Q]: Fact: landfills have a negative impact on the environment
[A]:
Which is a positive impact on the bio environment?