The Total Cost Curve for a Firm Can Be Derived

The total cost curve for a firm can be derived from isoquants and isocost lines by

A) varying the prices of capital and labor and keeping total expenditure constant.
B) varying production technologies, but keeping input prices and expenditure levels constant.
C) varying total expenditures while keeping input prices and production technology constant.
D) varying the price of either capital or labor while keeping total expenditures and production technology constant.