Correct Answer: D

Explanation:

Process costing is used when it is not feasible to identify individual units of production or specific jobs, typically due to the continuous and uniform nature of the production process. It applies to industries where goods are produced in a steady, uninterrupted flow and each unit is indistinguishable from the next.

The manufacture of liquid soap is a classic example: production is continuous, costs are accumulated across the entire process, and then averaged over a large number of identical units. Other costing methods such as job costing (used for unique, one-off jobs) or batch costing (used for discrete batches of identical items) are not suitable for this type of production.