Help please!! I need help quick it’s my final I can’t fail

Ibelieve the answer is c also i'm in k12 too

Geothermic gradient is the rate of increasing temperature with respect to increasing the depth in the earths interior. away from tech tonic plates boundaries, it is about 25-40 c/km (72-87 degrees f/mi) of depth near the surface in most of the world.

Answer decreased soil salinity;