Answer: The correct answer is capillaries
Explanation:
capillaries are tiny branched blood vessels that links arterioles to venules and allows exchange of nutrients and gases between the blood and its surrounding tissues
If untreated sewage gets into rivers, microorganisms decompose it. They use oxygen from the water for aerobic respiration. As a result there is less oxygen dissolved in water, so aquatic organisms such as fish and insects may be unable to survive.
Answer:
The cell theory developed most quickly due to the invention of the microscope. Robert Hooke was the first scientist who saw cells in cork. After this discovery, a wide numbered of researches were made and cell theory was developed. The basic cell theory explained that how every living thing was made up of cells. After this, a lot of additions have been made in the cell theory and today the cell theory is known to have five basic postulates.