What do scientists estimate is the approximate age of the planet earth? a. 660 million years b. 3.5 billion years c. 4.6 billion years d. 12.2 billion years

An atom of nitrogen had seven protons in its nucleus. how many electrons does it have

The terrestrial planets are characterized by having a a.) silicate core b.) iron-rich silicate core c.) iron-rich metallic core d.) none of these

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.