Sb-26 what information is most important when passing near a lighthouse

Most important information  when passing near a lighthouse is the water depth.
Today there are many complex navigation instruments,but in the past the lighthouse were the only navigation sailors had. However, the lighthouse still is very important in the navigation. There is an information chart on every lighthouse that gives information about  the location of the lighthouses and the depth of the water. With these information an experienced sailor can navigate even without modern instruments.

Letter c i’d say