What is marginalism?
A) the study of how much extra use is gained from incremental increases in the quantity of goods created, sold, or consumed
B) the market situation where supply and demand requirements of all buyers and sellers have been satisfied without creating surpluses or shortages
C) the ability of a good or service to satisfy one or more needs or wants of a consumer
D) a change in an activity's overall benefit that is caused by a unit change in the level of that activity while all other factors remain constant

Marginalism is the study of how much extra use is gained from incremental increases in the quantity of goods created, sold, or consumed.

Option: A

Explanation:

Marginalism is an important theory of economics. It is the study of quality of products for judging its power to serve extra use by increasing its number incrementally. Marginalism prevails in that condition where quantity of products slightly increase in respect of creation, selling and consumption.

Marginalism does not exist in the situation of no surplus or no shortage means in equilibrium condition. A good's capacity of giving extra service on extra use is called marginal service capacity or marginal productivity. For reaching the satisfaction level of buyers extra use of increased quantity of good is required.