How many times must the hashed index be probed (i.e. accessed) in order to return the result?

If instead the index was a B+ tree, how many times must the index be probed, starting at the root?

Databases usually contain large amounts of data and a DBMS is required to read data from disk whenever a query is executed. A database index is a data structure that

improves the speed of data retrieval operations by enabling the DBMS to read only a subset of all data from disk when answering a query.