Sit ups is probably the correct answer
<span>Severe depression that has a sudden onset or seems not to have any
external cause whatsoever is called major depression. Major
depression is sometimes referred to as </span>unipolar disorder or major
depressive<span> disorder (MDD); typical signs of MDD include
persistent feeling of sadness or a lack of interest in outside stimuli.</span>
Answer: Gasses are exchanged across the alveolar membrane.
The exchange of gasses takes place across the alveolar membrane of the lungs. Our respiratory system are composed of nose, pharynx, larynx, trachea, bronchi, and lungs (alveoli) where gas exchanges between the blood and external environment by diffusion. Moreover, during the gas exchange, the oxygen enters the blood while carbon dioxide enters the alveoli.
