Scientific research about the nitrogen cycle and water quality is mostvaluable to human populations with: afew sources of electricity. b. few sources of fresh water. c. large coastal populations. d. large amounts of farmland.

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?