Which of the following statements about the earth's atmosphere is true? it contains 21% oxygen. it contains 78% water vapor. it contains 21% carbon dioxide. it blocks all radiation from the sun.

What is called the "building block" of life?

What is the difference between an igneous, sedimentary and metamorphic rock

How are the reproductive cycles of a fungus and a pteridophyte similar? a)both organisms form fruiting bodies that produce diploid seeds. b)both organisms produce haploid spores and exhibit diploid and haploid stages. c)both organisms reproduce sexually when two haploid hyphae fuse. d)both organisms exhibit a diploid stage and are only able to reproduce asexually.