In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.

[Q]: Question: Which crust lies deep inside the ocean? Answer: oldest
[A]: Oldest crust lies deep inside the ocean.


[Q]: Question: When do weather balloons return to earth? Answer: when it bursts
[A]: When it bursts do weather balloons return to earth.


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