You use a Microsoft SQL Server 2012 database that contains two tables named
SalesOrderHeader and SalesOrderDetail. The indexes on the tables are as shown in the
exhibit. (Click the Exhibit button.)

You write the following Transact-SQL query:

You discover that the performance of the query is slow. Analysis of the query plan shows
table scans where the estimated rows do not match the actual rows for SalesOrderHeader
by using an unexpected index on SalesOrderDetail.
You need to improve the performance of the query.
What should you do?

A.
Use a FORCESCAN hint in the query.

B.
Add a clustered index on SalesOrderId in SalesOrderHeader.

C.
Use a FORCESEEK hint in the query.

D.
Update statistics on SalesOrderId on both tables.

Explanation:
http://msdn.microsoft.com/en-us/library/ms187348.aspx