The correct answer is - B. shifting cultivation.
In the commercial farming, which is used in the developing and well developed countries, there's not really a space for the shifting cultivation, nor there's a real need for that.
The shifting cultivation is mostly practiced in the poor countries, where the subsistence farming is dominant. The purpose of the shifting cultivation is to leave the soil time for recuperation and get back to better fertility levels, and that is done by changing the plants every year, and because every plant is using different nutrients, the soil can be used for longer periods of time.