I actually thought this one was easy. I know that the term balanced is the B in B tree.

Reason because the way the pages and indexes work in Sybase and SQL Server for example with a root node, intermediate nodes and leaf node.

Very noddy diagram warning:

There should always be the same number of jumps to pages no matter where the data is stored on table via index. Oracle has other types of storage available as well as B tree.

I think MS Book on SQL Server internals may have a reference to this.

I usually have to have a good think about the questions this one I knew the answer straight away.