Option 1 -> Cost Function shows the relationship between output and total cost, not inputs and outputs.
Option 2 -> Production function directly defines the relationship between inputs (labor, capital, etc.) and outputs produced.
Option 3 -> Opportunity cost represents the value of the next best alternative foregone, not an input-output relationship.
Option 4 -> Revenue function shows the relationship between quantity sold and total revenue, not inputs and outputs.
Hence, Option 2: Production function -> A production function is a mathematical expression that shows the maximum output that can be produced from different combinations of inputs (factors of production like labor, capital, raw materials, etc.). For example, Q = f(L, K) where Q is output, L is labor, and K is capital. It is fundamental to understanding how firms transform resources into goods and services. -> correct