When an arborist prunes a limb off a valuable tree, he or she ...

[xclash]

When an arborist prunes a limb off a valuable tree, he or she usually paints the cut surface. The primary purpose of the paint is to
A) minimize water loss by evaporation from the cut surface.
B) improve the appearance of the cut surface.
C) stimulate growth of the cork cambium to "heal" the wound.
D) block entry of pathogens through the wound.
E) induce the production of phytoalexins.

[clippers!]

I chose D and got the answer, hope that helps.