What is the name for the level of crop output from a given level of input?

Subsistence farming is the level of crop output from a given level of input.

Explanation:

Farmers grow "food crops" to feed themselves and their families. There will be little or no surplus trade as they get output for whatever input. This process is called subsistence agriculture or subsistence farming. They raise the livestock for their own’s use but not for any trade activities. For example: nomadic people raise a cow to provide milk to their own family. They give sufficient and necessary food for the cow an get the required quantity to suffice their family.

The correct answer should be brand c.

Answerland;