Given a scientific passage and an answer, generate a question for the given answer.

Ex Input:
Passage: Density is defined as the mass of an object divided by its volume. Propose a unit of density in terms of the fundamental SI units. Answer: volume

Ex Output:
Density is defined as the mass of an object divided by its what?

Ex Input:
Passage: The biological electron transport chain provides for an orderly, stepwise transfer of electrons. Both NADH (reduced nicotinamide adenine dinucleotide) and FADH2 (reduced flavin adenine dinucleotide) are energyrich molecules that liberate a large amount of energy during oxidation. Free energy released during the transfer of electrons from either of these molecules to oxygen drives the synthesis of ATP (adenosine triphosphate) formed during respiratory metabolism. The reactions are as follows:. Answer: oxidation

Ex Output:
The biological electron transport chain provides for an orderly, stepwise transfer of electrons. both nadh (reduced nicotinamide adenine dinucleotide) and fadh2 (reduced flavin adenine dinucleotide) are energy rich molecules that liberate a large amount of energy during what?

Ex Input:
Passage: Vertebrates. From the smallest of fish to us. One of the main features we all have in common is our backbone. Vertebrates describes main biological features of fish, amphibians, reptiles, birds, and mammals. Answer: backbone

Ex Output:
Vertebrates. from the smallest of fish to us. one of the main features we all have in common is our what?