The use of rivers for irrigation in agriculture began in about a. 10,000 bce b. 6,000 bce c. 2,000 bce d. 500 bce

Iam pretty sure it is c. 2000 bce

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.