Step 1: Analyzing and Matching Each Term:
(A) Oligopoly: This is a market structure characterized by a small number of large sellers. The key is "few" sellers. This matches with definition (IV).
(B) Marginal Cost: In economics, marginal cost is the change in the total cost that arises when the quantity produced is incremented by one unit. It is the change in total cost per unit of change in output. This matches definition (III).
(C) Duopoly: This is the most basic form of oligopoly, a market dominated by exactly two firms. This matches definition (II).
(D) Cost function: This is a mathematical function that relates the total cost of production to the level of output. It specifies the minimum cost required to produce a given quantity of output. This matches definition (I).
Step 2: Forming the Correct Combination:
The correct pairings are:
A $\rightarrow$ IV
B $\rightarrow$ III
C $\rightarrow$ II
D $\rightarrow$ I
This corresponds to the sequence (A)-(IV), (B)-(III), (C)-(II), (D)-(I).
Step 3: Final Answer:
Looking at the options, option (B) matches our derived sequence.