What challenges do one crop agriculture create for farmers in colombia

The correct answer for this question is this one:

"The challenges one crop agriculture create for farmers in Colombia is that they have to think of strategies to do agriculture. They encountered a lot of challenges that will make agriculture successful. They have to take into account the things that is very important in agriculture."

Answer the collision of tectonic plates;

Well, a and b together would be negative. b alone would also be negative.