Crabs are organisms that have five pairs of legs. In certain species of crabs, the fifth pair of legs has a flattened, paddle-like shape. Which of the statements below best explains how this adaptation has evolved?

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.