Salesforce best practices strongly recommend using only one trigger per sObject. This approach consolidates all trigger logic, preventing issues with unpredictable execution order that can arise when multiple triggers exist for the same object. The single trigger should handle all necessary DML events (e.g., before insert, before update, before delete).

Furthermore, triggers should be "logic-less." The trigger's role is to delegate the processing to a handler or helper Apex class based on the context (e.g., Trigger.isInsert, Trigger.isDelete). This makes the code more modular, reusable, and easier to test and maintain.

1. Apex Developer Guide

"Triggers": The official documentation states

"There can be multiple triggers for a particular object

but you should try to have only one trigger for each object." This supports unifying the triggers.

2. Apex Developer Guide

"Trigger and Bulk Request Best Practices": This section explicitly recommends

"Use one trigger per object." It further explains

"If you develop multiple triggers for a single object

you have no way of controlling the order of execution." This directly supports option A and refutes option D.

3. Apex Developer Guide

"Trigger Context Variables": The guide details how to use context variables like isInsert and isDelete within a single trigger to invoke different logic paths

which is the mechanism for implementing a unified trigger that calls helper classes. This supports the combination of options A and C.

4. Trailhead

"Apex Triggers" Module

"Trigger Best Practices" Unit: This official learning resource emphasizes two key principles: "One Trigger Per Object" and "Logic-less Triggers

" which directly correspond to options A and C. It advises creating helper classes to contain the logic that the single trigger will then call.