A B D is correct
Explanation
Knowledge-Centered Support (KCS) is a methodology that enhances how customer service and support teams access and use knowledge to deliver greater value to customers, employees, and stakeholders. Some of the benefits that can be expected from KCS adoption are:
Increased call deflection: KCS enables customers to find answers to their questions or issues through self-service channels, such as knowledge bases, communities, or chatbots. This reduces the number of calls or emails that reach the support team and improves customer satisfaction and loyalty.
Reduced issue resolution time: KCS allows agents to access and update knowledge articles as part of their support process. This helps them find the information they need to solve problems faster and more accurately, as well as share their knowledge with other agents and customers.
Optimized use of resources: KCS reduces the need for dedicated knowledge management roles or processes, as knowledge creation and maintenance are integrated into the support workflow. This frees up time and resources for other value-added activities, such as product improvement, innovation, or training....

David is right: " Empowering your customers to access those same answers through
self-service channels means increased call deflection and an effortless customer
experience."
https://www.salesforce.com/content/dam/web/es_mx/www/documents/service-cloud/resources/Salesforce_Knowledge_Datasheet.pdf

A,B,D

KCS increases call deflection: https://www.salesforce.com/video/305885/
It does not reduce support channels. (It often increases them)