What does the `Connection: keep-alive` header achieve in HTTP/1.1?

1. A It keeps the target application server running in a low-power mode to ensure that it can respond to subsequent incoming requests with zero initial computational delay.
2. B It prevents the browser from closing the current active tabs, ensuring that the user's session state remains persistent even if the underlying network connection is temporarily lost.
3. C It significantly increases the internal server-side timeout period for a specific request, allowing for the delivery of exceptionally large or complex data payloads.
4. D It instructs the server not to close the underlying TCP socket after sending a response, allowing the same connection to be reused for multiple subsequent requests.