D
https://developer.salesforce.com/docs/atlas.en-us.change_data_capture.meta/change_data_capture/cdc_intro.htm


With Option C you introduce way too much complexity and maintainance. How would you know the behaviour of other system and take responsibility to have it updated in salesforce? and why even?

With Option D External data can be updated in real time and stays fresh after capturing changes with Change Data Capture event notifications in near real-time.
This is not very complex as well. CDC is used for a simple, one-way, outbound, data broadcast from Salesforce. For example, say that an external system wants to receive a broadcast every time a Salesforce account record is created, updated, deleted, or un-deleted.
You can subscribe to change events with CometD, Pub/Sub API, or Apex triggers. CometD is a messaging library that enables listening to events through long polling and simulates push technology. Pub/Sub API is based on gRPC and HTTP/2 and enables clients to control the volume of event messages received. Apex triggers for change events are similar to Apex triggers on platform events....