How can sand dunes be re-built?me

The basic steps are simple but careful planning is needed. Sand dune restoration should be designed to create a dune that matches the existing natural dune pattern in the area. You can help speed up nature's work by using sand fences and dune plants to collect sand more rapidly. Or in a different way, wind would bring more sand to create a dune. hope this helped, have an amazing day :)

If its history of, then b) because a) implies only present day (now)