The InnoDB engine has a feature known as clustered indexes. Which three statements are true about clustered indexes as used in InnoDB?（）
- AA primary key must exist for creation of a clustered index
- BA clustered index allows fulltext searching within InnoDB
- CThe first unique index is always used as a clustered index and not a primary key
- DA clustered index provides direct access to a page containing row data
- EIf no indexes exist, a hidden clustered index is generated based on row IDs
- FA primary key is used as a clustered index
- GA clustered index is a grouping of indexes from different tables into a global index for faster searching