Forests do not

a.

protect the soil from erosion

c.

yield useful products

b.

provide habitats for many species

d.

increase soil salinization

The roots of trees helps hold the soil together, so it's not a
Forests do in fact, yield useful products, fruits, lumber, animals to hunt, medicine tree, so it's not b
Forests do provide a habitat for many animals, so it's not c
SO the answer must be D. For reference, soil salinization is the process in which salt content increases in the soil.

I think the answer is D.increase soil salinization

The sun's parallax would be 180 degrees, greater than which you can't get.  so a. would be your anwser 

Answer were lower;