In the nineteenth century, with westward expansion of railroads,
popularity as fuel.

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme

answer: wheres the options

explanation:

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.