Which statement correctly describes a chemical reaction? reactants come out of a reaction. energy is always released. bonds between atoms break and new bonds form. products go into a reaction.

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.

How are gene and protein sequences used to classify organisms?

What have we learned from fossil evidence about evolution? a) it is an abrupt change. b)the process is observable. c) it takes place during one lifetime only. d)the most complex traits are always selected.