You design a Business Intelligence (BI) solution by using SQL Server 2008. The data warehouse contains a table named Employee Dimension.
The table contains the following three attributes:
-EmployeeID
-EmployeeName
-ReportsTo

The ReportsTo attribute tracks the EmployeeID attribute of the manager that an employee reports to.
You need to ensure that sales data of only managers and the names of all employees reporting to each of these managers are displayed. You want to achieve this goal by using a hierarchy model that provides the best possible performance when the data warehouse is queried.
Which hierarchy model should you use?

A.
Ragged Hierarchy

B.
Balanced Hierarchy

C.
Non-Natural Hierarchy

D.
Parent�Child Dimensional Hierarchy

Explanation:
Tip: "hierarchy model … best possible performance" = "ParentChild"

http://msdn.microsoft.com/en-us/library/ms174846.aspx
Defining a Parent-Child Hierarchy
A parent-child hierarchy is a hierarchy in a standard dimension that contains a parent attribute. A parent attribute describes a self-referencing relationship, or self-join, within a dimension main table. Parent-child hierarchies are constructed from a single parent attribute. Only one level is assigned to a parent-child hierarchy, because the levels present in the hierarchy are drawn from the parent-child relationships between members associated with the parent attribute. The position of a member in a parent-child hierarchy is determined by the KeyColumns and RootMemberIf properties of the parent attribute, whereas the position of a member in a level is determined by the OrderBy property of the parent attribute. For more information about attribute properties, see Attributes and Attribute Hierarchies.
Because of parent-child relationships between levels in a parent-child hierarchy, some nonleaf members can also have data derived from underlying data sources, in addition to data aggregated from child members.