instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
The bird ancestor that lived in trees developed wings, which is commonly associated with birds.
answer:
The bird ancestor that lived in trees developed what feature commonly associated with birds?


question:
Processing of filtrate in the proximal tubule helps maintain the ph level in body fluid.
answer:
Processing of filtrate in the proximal tubule helps maintain what level in body fluid?


question:
Rapid decrease is a trend that is occurring involving the extent of arctic sea ice in summer.
answer:
What trend is occurring involving the extent of arctic sea ice in summer?