To answer this question, we need to understand the term "upsetting" in the context of operations.
Option A) Casting - Casting is a process where molten metal is poured into a mold to create a desired shape. Upsetting is not typically associated with casting.
Option B) Turning - Turning is a machining process where a cutting tool is used to remove material from a rotating workpiece. Upsetting is not typically associated with turning.
Option C) Drilling - Drilling is a process of creating a hole in a workpiece using a rotating cutting tool. Upsetting is not typically associated with drilling.
Option D) Forging - Forging is a manufacturing process where a metal is heated and shaped by applying compressive forces. Upsetting is a term used in forging to describe the process of increasing the diameter of a workpiece by compressing it between dies.
Therefore, the correct answer is D) Forging. Upsetting is the term used in the forging operation.