What do the runway centerline lights changing from white to alternating red and white indicate?

The lights changing from white to alternating red and white indicate that the aircraft is near the end of the runway, specifically when there are 3,000 feet of runway remaining. This is an essential visual cue for pilots during landing, as it helps them assess their position on the runway and their distance from the end. Understanding these light signals allows pilots to make informed decisions about their landing approach and potential need for a go-around if they are unable to safely land within the remaining runway.

Knowing these distances accurately contributes to maintaining safety during landing operations. The other options represent distances that are either greater or less than what the alternating lights signify, which is why they do not align with this specific indication.