Step 1: Understanding the Concept:
The question refers to a pre-trial procedure under the Code of Civil Procedure, 1908, which allows parties to obtain information from each other to narrow down the facts in dispute and prepare for trial.
Step 2: Detailed Explanation:
Let's examine the terms:
\begin{itemize}
\item (D) Discovery: This is the broad, overall process by which parties obtain evidence from each other. It includes several tools.
\item (C) Interrogatories: This is a specific tool of discovery. It consists of a set of written questions served by one party to another, which must be answered in writing and under oath. The description in the question—"administer to his adversary a series of questions"—perfectly defines interrogatories. This process is governed by Order XI, Rule 1 of the CPC.
\item (A) Question petition and (B) Question pamphlet are not recognized legal terms for this procedure in the CPC.
\end{itemize}
While interrogatories are a part of discovery, the specific term for the series of questions is "interrogatories."
Step 3: Final Answer:
The process of administering a series of written questions to the opposing party is called serving Interrogatories.