1. Salesforce Help Documentation, Salesforce Data Entry Source: This document explicitly describes the functionality shown in Option C. It states, "The Salesforce Data entry source lets you choose a Salesforce object, then filter the records that enter a journey... A journey can be triggered when a record is created or updated." This directly supports using a Salesforce object creation event as the journey trigger. (Salesforce Help, Marketing Cloud, Journey Builder, Entry Sources section).
2. Salesforce Help Documentation, Use Salesforce Data in Journey Builder: This guide details the configuration process. It outlines the steps: "Select the Salesforce Data entry source... Choose a Salesforce object... Select who to inject... Set entry criteria... Select entry data." The screenshot in Option C is a direct representation of these configuration steps for the specified custom object. (Salesforce Help, Marketing Cloud, Journey Builder, Audiences section).
3. Salesforce Help Documentation, Entry Sources: This page provides an overview of all available entry sources. It differentiates the "Salesforce Data" source, which is integrated via Marketing Cloud Connect for declarative setup, from the "API Event" source, which is used for transactional sends triggered by an API call. This distinction highlights why the Salesforce Data Event is the lower-effort solution for this use case. (Salesforce Help, Marketing Cloud, Journey Builder, Entry Sources section).