You execute the following code:

You create a nonclustered index named IX_CustomerName on the CustomerName column.You execute the following query:

You need to reduce the amount of time it takes to execute the query.
What should you do?

A.
Partition the table and use the CustomerName column for the partition scheme.

B.
Replace IX_CustomerName with a clustered index.

C.
Replace LEFT(CustomerName ,1) = ‘a’ with CustomerName LIKE ‘a%’.

D.
Replace LEFT(CustomerName ,1) = ‘a’ with SUBSTRING(CustomerName ,1,1) – ‘a’.

Explanation:
http://msdn.microsoft.com/en-us/library/ms179859.aspx
http://msdn.microsoft.com/en-us/library/ms187748.aspx