In this task, you are given a sentence and a question, you would be asked to create the answer which is contained in the sentence provided.

[Q]: Sentence: Calculations are described showing conversions between molar mass and density for gases. Question: Calculations are described showing conversions between molar mass and what for gases?
[A]: density


[Q]: Sentence: Ribosomes are the only organelles that prokaryotic cells have. Question: What are the only organelles that prokaryotic cells have?
[A]: ribosomes


[Q]: Sentence: The bird ancestor that lived in trees developed wings, which is commonly associated with birds. Question: The bird ancestor that lived in trees developed what feature commonly associated with birds?
[A]:
wings