You are developing an application that includes a class named Order. The application will store a collection of Order objects. The collection must meet the following requirements: ✑ Internally store a key and a value for each collection item. ✑ Provide objects to iterators in ascending order based on the key. ✑ Ensure that item are accessible by zero-based index or by key. You need to use a collection type that meets the requirements. Which collection type should you use?