Nitrogen is essential to life a. it is needed for building the proteins needed for cells. b. it is the molecule around which all the molecules of life are built. c. it is needed for making carbohydrates and lipids. d. it is the most common element.

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?