Final answer:
Slurred speech is a delayed sign of a concussion, which is a mild traumatic brain injury.
Step-by-step explanation:
The delayed sign of a concussion among the options provided is slurred speech. A concussion is a mild traumatic brain injury that can result from a blow to the head or violent shaking of the head and body. While loss of consciousness can occur immediately after a concussion, it is not a delayed sign. Vertigo and blurred vision can also be symptoms of a concussion, but they may be experienced immediately or shortly after the injury.