Why is "Deforestation" (cutting down trees) a leading cause of soil becoming infertile and blowing away?
(A) Trees provide shade that keeps the soil from melting.
(B) Tree roots act like "nets" that hold the soil together and prevent it from being washed away by rain.
(C) Trees produce a special glue that sticks the sand together.
(D) Cutting trees makes the wind blow in circles.