Comprehensive and Detailed In-Depth Explanation:

A warehouse order in SAP EWM is a collection of tasks grouped for execution. Option B ("Warehouse tasks") is correct because a warehouse order always contains one or more tasks (e.g., picking, putaway), created based on warehouse requests. Option D ("Physical inventory items") is correct as warehouse orders can include tasks for physical inventory counts, configured via SPRO: SCM Extended Warehouse Management > Physical Inventory. Option A ("Warehouse requests") is incorrect because requests are the source for tasks, not part of the order itself. Option C ("Wave items") relates to wave management, not directly to warehouse orders.