Plz what is mass per unit volume called?

a)density
b)gravity
c)temperature
d)weight

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.

Which of the organisms listed below performs nitrogen fixation? a. legumes b. plants c. bacteria d. fungi

10. in which phase will crossing-over occur? a. mitosis b. metaphase ii c. prophase i d. meiosis ii