What is a fuel? In science ​

The circles, or orbits, for electrons are called energy levels. each level can hold only a certain number of electrons. add electrons to each level until you can't add any more. how many electrons can each level hold?

Which macromolecule catalyzes chemical reactions this be considered enzyme chemical reactions thus he considering enzymes

Me.henley said, “in the rat race we call life, only the strong will survive.” he may have been referring to