Describe the structure of dna? what are the chemical units that come together to make a molecule of dna?

Someone me with this: a mineral' is determined by its actomic structure.

9. the history of life on earth is recorded in

Which of the following best describes the purpose of the parathyroid hormone? a. it decreases the blood calcium level and decreases blood phosphorus level. b. it decreases the blood calcium level and increases the blood phosphorus level. c. it increases the blood calcium level and increases blood phosphorus level. d. it increases the blood calcium level and decreases blood phosphorus level.