Which of the following is not true concerning the impact of volcanoes? a. acid rain can result from volcanic eruptions. b. tephra are a combination of water and rubble. c. damage can continue for years after the initial eruption. d. the volcanic explosion is the pyroclastic flow.

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.