A virus is made up of remnants of cells in a living host (of animals, plants or bacteria), infecting cells and forcing them to reproduce at a fast rate, thousands of identical cells (same of the original virus). Viruses are microscopic and can either be single- or double- nucleic acid. They are enveloped with lipids or fatty materials and proteins. So outside of the virus contains lipids or a protein, that is letters C. and D. from the choices above.