It may be harmful when people compete to see who can hold their breath the longest underwater. Without oxygen, brain cells *

Without oxygen, brain cells cannot make enough ATP.

Explanation:

Hypoxia is a condition that occurs due to low levels of oxygen. In conditions such as holding of breath for a long period of time, the oxygen carrying haemoglobin ( oxyhaemoglobin) breaks down, releasing oxygen to the body tissues, which constantly consumes oxygen keeping the levels low.

In the presence of decreased oxygen supply, autoregulatory mechanisms that control the blood flow to the brain by adjusting the diameter of the arterioles fails. The consequent rapid decrease in the cerebral blood supply leads to hypoxia and lack of glucose( decreased ATP production). If severe hypoxia is sustained for more than a few minutes, this could lead to irreversible brain damage.

Therefore, It may be harmful when people compete to see who can hold their breath the longest underwater.

away from the curb

explanation:

the wheels would then hit the curb if it started to rolling, decreasing the chance of an accident.