Plz tell me all the one that are blank. i dont get it the first one is just an example.

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.

In dna, only the_ varies from one nucleotide to another. base phosphate sugar amino acid

Most crimes involve some evidence relating to the human body; for that reason, what related science is frequently used in forensic investigations? a)psychiatry b)physics c)botany d)biology