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

[Q]: Resonance is the term for the use of two or more lewis structures to represent the covalent bonding in a molecule.
[A]: What is the term for the use of two or more lewis structures to represent the covalent bonding in a molecule?


[Q]: Phospholipids are the main component of the cell membrane.
[A]: What is the main makeup of the cell membrane?


[Q]: Portal veins carry blood between pairs of capillary beds.
[A]:
Portal veins carry blood between what?