In low-rainfall areas, huge shifting sand dunes are commonly found, particularly near human habitations. Techniques of afforesting the shifting dunes needed to be implemented. These techniques consist of___________?

A. Treatment of shifting sand-dunes by fixing barriers in parallel stripes or in a chess-board design, using the local shrub material starting from the crest of the dunes to protect the seedlings from burial or exposure by the blowing of sand.
B. Protection against biotic interference
C. Both a & b
D. None of these