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In natural selection, what is actually “selected? ” a) alleles are directly selected b) genotypes are directly selected c) phenotypes are directly selected d) entire populations are directly selected

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.

When fossil fuels are burned, carbon dioxide is released. how does this gas impact the environment?