#genral science
☆▪photosynthesis increases concentration of oxygen in air, which is necessary for
a living organism
b. fossils
c. birds only
d. animals

Regarding most of the narrator’s story, which word best describes the tone?

Several billion years ago which gas was the least prevailant in the atmosphere

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?