You plan to create a unique nonclustered index on the CustomerID， LastName， and FirstName columns of the CustomerData.Customers table in the CRM database. To aid in estimating the space requirements for the index， you identify the following variables：

You need to identify the most significant additional variable that will increase the estimated index size. Which additional variable should you identify？（）

A.current number of rows
B.null bitmap
C.fill factor
D.automatically generated uniqueifier value