In a Work Queue, the lock symbol (Option B) typically indicates that a case is currently being processed. This is because the lock symbol is commonly used to represent that an item is 'locked' or 'in use,' which aligns with the concept of a case being actively worked on. Other symbols like the checkmark (Option A), ellipsis (Option C), or flag (Option D) do not usually convey the same meaning of a case being currently processed.