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

[Q]: Gastric emptying is regulated by both the stomach and the duodenum.
[A]: Gastric emptying is regulated by both the stomach and what other digestive structure?


[Q]: Resistors connected end to end are said to be in series.
[A]: Resistors connected end to end are said to be in what?


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