Chemical and gaseous exchange takes place only across capillary walls
Sorry for the late answer but I hope that's still help !
Explanation:
"Life on earth is classified into three domains: Bacteria, Archaea and Eukarya. The first two consist completely of single-celled microbes."
Hormone is a substance that directly involve in cellular communication within the human body.
Explanation:
A hormone is a restrictive substance created in an organism and transported in tissue fluids like blood or sap to stimulate specific cells or tissues into action.
It is a synthetic substance with result thereto of an animal or growth regulator.
It is a person's sex hormones as control to influence behavior or mood.
Approximately 72 hours (3 days)
Answer: Nucleotides
Nucleotides is the correct answer.