The correct answer is C) They used fencing to protect their crops from cows.
The law of the open range was a problem for farmers in that they used fencing to protect their crops from cows.
Open range means that cattle roamed free in the land, regardless of private property. The law of open range mad farmers to put fences around their private land to keep cattle out of the property. This represented a problem for the resources needed to invest in fences, limiting the pass of the cattle.