Identify in general what do all elements in the same family have in common

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.

What does the number 18.9984 represent in the image?

Adistinctive characteristic of mammals that is not observed in other vertebrates is