This is because ES is a resource-intensive application that requires a dedicated search head with sufficient CPU and memory. Installing ES on the existing search head may cause performance issues and conflicts with other applications. Deleting the non-CIM-compliant apps from the search head is not recommended, as they are mission-critical for the site. Increasing the number of CPUs and amount of memory on the search head may not be enough to handle the load of ES and other applications. Therefore, option B is the most suitable answer. You can find more information about installing ES on this web page1.