A population is living off a secure subsistence base, eating plants and animals caught by hunting, fishing, and gathering. The population expands, and as it does, it puts pressure on the resource base, forcing people to eat "third-choice" foods, especially grains. They discovered that the grain responded to human efforts to increase yields, and came to rely increasingly on it. This scenario would fit best with which of the following theories of agricultural development?
A. Broad spectrum foraging theory.
B. Conflict theory.
C. Resource base transformation theory.
D. Population pressure theory.

The scenario in the question best fit the broad-spectrum foraging. Broad-spectrum foraging is the term used to refer to the human subsistence shift in which foragers broadened their resource base to encompass a wide array of foods that were previously ignored in an attempt to overcome food shortages. The broadening of food base from hunting, fishing to include grains is an example of broad-spectrum foraging.