Why are no rocks found that date from the first 800 million years of Earth's
existence?
O
A. All the rocks from that time period have been destroyed by plate
movements,
O
B. They have all been buried too deeply under newer rocks.
O
c. Earth was too hot to have solid rocks at that time.
O
D. They were all destroyed by a comet impact.

6. in the dna double helix, how are the two strands of dna held together? a. chemical bonds between base pairs hold the two strands of dna together. b. hydrogen bonds between the base pairs hold the two strands of dna together. c. hydrogen bonds between sugar groups and phosphate groups hold the two strands of dna together. d. chemical bonds between sugar groups and phosphate groups hold the two strands of dna together.

The cluster of developing cells from conception until birth is called an

Which statement describes compounds a. compounds are made of one type of atom. b. compounds cannot be represented by models. c. compounds are represented by chemical formulas. d. compounds cannot be broken down into simpler forms.