Deforestation most directly results in
(1) an increase in oxygen in the atmosphere
(2) a decrease in soil erosion
(3) a decrease in biodiversity in the area
(4) an increase in the absorption of carbon dioxide

Deforestation is the destruction of forests: it means that there will be less trees, not more. This also means less oxygen and more carbon dioxide in the atmosphere- the opposite of options 1 and 4.

The correct answer is (3) a decrease in biodiversity in the area - less trees means less species that can live in and around them. 

I would have to go with C it makes more sense to me