Read the sentence from the section “Water Sphere.” However, around three-quarters of all the fresh water on Earth remains locked up in the cryosphere.

What is the meaning of the phrase “locked up’ as it is used in the sentence?

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.