You are responsible for managing the database schema for an order entry application in a SQL Server 2005 database. After a design review， a member of the development staff asks you to add a new column named CommissionRate to the Product table. Because the actual commission rates for all products are not known at this time， each product has a default commission rate of 12 percent. The rate can be modified as necessary. You add the new column. You need to configure the table to assign the default value as efficiently as possible. What should you do？（）

• A、Create an INSERT trigger to assign the default value to each item in the table.
• B、Create a CHECK constraint to validate the data and to assign the default value to each item in the table.
• C、Create an UPDATE trigger to update the default value for each new item in the table.
• D、Create a DEFAULT constraint to assign the default value specifying the WITH VALUES argument.