Question

a concussion is—
a temporary impairment of brain function.
the blood trapped in the skull as a result of a violent blow to the head.
long - term memory loss suffered by someone who received a violent blow to the head.
a weakening of the blood vessels in the brain.

Explanation:

A concussion is defined as a temporary disruption of brain function caused by a blow or jolt to the head. The other options describe different conditions: trapped blood refers to a hematoma, long-term memory loss is not a defining feature of concussions, and weakened blood vessels are unrelated.

Answer:

A temporary impairment of brain function.