"Swidden" or "slash-and-burn" agriculture is a form of subsistence farming practiced all over the world, although it is most widely found in tropical regions such as Amazonia. One of the oldest forms of agriculture, swidden involves clearing the forestation and growth in a desired field with axes, then burning the stumps to eliminate obstructions and enhance the soil. This practice has harmful effects of rainforests in which it is practiced and does not produce high yield for its farmers, causing ecological and economic problems.

Corn is the only subsistence crop of the presented options. Tobacco, cotton, and rice are all high intensive plantation crops. Tobacco, cotton, rubber, and papyrus are also not edible, therefore disqualifying them from being considered subsistence crops.

Subsistence agriculture involves food production mainly for the family. A farmer will grow most everything that the family would consume, and anything leftover will go to the local community rather than to a big market.

By definition, a subsistence crop is a crop that is grown primarily for the purpose of feeding/sustaining farmers and their families, with any surplus going towards trade. Of the following answer choices, rice is the only one that can be characterized as a subsistence crop, as rice is a staple food in many agricultural regions. 

A "cash crop" is an agricultural crop that is purposely made strictly to be sold in a market environment for as much money as possible. Most cash crops, which include cotton, opium, grains, and many other products, are grown in a monoculture environment, where they are the only product grown on a piece of land. By their nature, cash crops are not a form of subsistence farming, as they are always produced to be used beyond a grower's own home and family.

When farmers grow a few lucrative crops, they cash cropping. Cash cropping involves growing one or a few crops that can be sold for a relatively high price. 

A cash crop is a crop like coffee or tobacco; something that is grown for profit and to meet some luxury rather than to sustain the population. Cash crops are primarily grown on plantations in the developing world. Cash crops, while generally grown in the developing world, are most often exported to the developed world.

Plantation agriculture is defined by the production of one or more usually cash crops on a large swathe of land. It is most common in tropical climates where cash crops generally grow more naturally.

Mixed-crop farming, livestock ranching, dairy farming, and grain farming are all historically prevalent in the United States of America.

“Hydroponics” is the name given to the method of growing crops in nutrient solutions instead of in soil. This allows food to be grown in arid climates and increases the geographic range in which many crops can be grown. It is common, for example, in desert climates where the soil is harsh and unforgiving.