In the human respiratory system, gas exchange occurs across the cells of the alveoli. Alveoli or an alveolus is the deepest part of the human respiratory system. This part of the respiratory system is a place where gas exchange between oxygen and carbon dioxide occurs from inhaled air to the blood cells<span>.</span>
D) Connective tissue. Skeletal muscle Striated muscle. It is under the person's voluntary control
B. All birds have feathers and hollow bones, but not all birds fly (ostrich, emu, kiwi, etc).
<span>Carrie proteins.................... sorry you have to have a minimum of 20 characters;)</span>
