Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

[EX Q]: Molar masses can be used to determine the mass of a quantity of material.
[EX A]: What can be used to determine the mass of a quantity of material?

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

[EX Q]: Certain characteristics are frequently inherited together because of linkage.
[EX A]:
Certain characteristics are frequently inherited together because of what?