What are characteristics of an efficient bitmap index?

a$.$ Each bucket initially has one block. Any additional blocks are allocated and linked to the initial block.

b$.$ The WHERE clause may specify any values in upper case. The column used in a WHERE clause may contain mixed upper and

lower case characters.

c$.$ The database can quickly determine the block containing a table row from the index row number. Any indexed column contains

relatively few distinct values.

d$.$ Indexes change only when primary key values are updated. Physical indexes change whenever a row moves to a new block.