X-1's waterproof, sweatproof, weatherproof earphones such as the momentum, the ultralight in-ear headphone, were developed for athletes and sports enthusiasts. the momentum would be best classified as a(n)

the cell theory states that all living things including animals, as well as plants, are made of cells.

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.