How can i use "contour plowing" in a sentence?

Drastic boundary changes can occur for all of the following reasons except for a. a shift in the way a river flows b. the collapse of a government system c. a conflict between two neighboring groups d. one country's decision to sell land to another country select the best answer from the choices provide

2/6 of be by to 2/6 is to 24/72 ?

Because its government strictly controls its economy, north korea has a economy. a. command b. mixed c. traditional d. free market