You are to select one of the choices for an indexing structure when used under the conditions indicated.
The system will QARRAY[QUERYTYPE], when stored SARRAY[STORAGE], working on a DARRAY[DATABASETYPE].
A Closed Hash Table is always great for exact-match queries, and always terrible for range queries.
A Linear Index is bad for dynamic databases. It is a little more efficient than the alternatives for static databases.
The B+ Tree is great on disk, but has too much overhead to be practical for in-memory applications.
A balanced BST is not good on disk, but works well for in-memory applications.