The most effective and standard method to meet this requirement is by using the InitiateRenewal invocable action, which is a core feature of Salesforce Revenue Cloud. This action is specifically designed to start the renewal process from an Account or Contract. By placing this action within a screen flow, a consultant can create a guided, user-friendly experience. Exposing this flow as a quick action on the Account or Contract record page provides the "one-click" capability for sales reps to generate a renewal opportunity and quote, populated with the customer's active, renewable assets.

B. An Apex trigger provides full automation based on a system event (approaching end date), which contradicts the requirement for a user-initiated action by a sales rep.

C. This approach is inefficient as it requires a sales rep to navigate to and update individual asset records, failing the "one-click" renewal requirement for an entire subscription.

1. Salesforce Help Documentation, Flow Core Action for CPQ: Initiate Renewal: This document explicitly describes the Initiate Renewal action. It states, "Initiate the renewal process for a contract or account. This action is available in API version 57.0 and later." It details the required input, which is the recordId of the Account or Contract, confirming its use on these record pages.

2. Salesforce CPQ & Billing Developer Guide, Invocable Actions for CPQ: This guide lists the initiateRenewal(requests) method as a standard invocable action. It confirms that this is the officially sanctioned programmatic entry point for starting the renewal process, which can be called from tools like Flow Builder.

3. Salesforce Help Documentation, Launch a Flow from a Quick Action: This guide provides the standard procedure for making a flow accessible to users directly from a record page. It details how to create an action of type "Flow," select the appropriate flow, and add it to the page layout, which fulfills the implementation part of the correct answer.