Macromolecules are formed by combining single units , called , together to form a chain , called monosaccharides; proteins monomers; polymers atoms; elements

Which type of respiration takes place when there is no oxygen present

Long-period comets come from the oort cloud particles in earth’s atmosphere material from the asteroid belt the kuiper belt

Ihave no idea how to solve these. plus there's another question that is 2) a 10 kilogram meteorite is collected in space and brought back to earth. it is composed of 1.25 kg of uranium-238 and 8.75 kg of lead-206. how many u-238 half lives have passed? what is the approximate age of the meteorite?