Why are plants found at the beginning of a food web

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.

You find a fossil that you are sure shows evidence of bipedalism. you know this because which of the following anatomical traits is present? a. thighbones that angle in toward the knees b. a narrow pelvis c. opposable hallux d. posterior position of the foramen magnum

Nitrogen-14 and nitrogen-15 are isotopes of the same element. how do these two isotopes differ? a. they have different numbers of nuclei. b. they have different numbers of protons. c. they have different numbers of neutrons. d. they have different numbers of electrons.