You are designing an upgrade strategy for a Windows Azure application that includes one web role with one instance.  You have the following requirements：   - Test the application on the Windows Azure platform.   - Ensure that application upgrades can be rolled back.   - Ensure that upgrade and rollback processes do not cause downtime.    You need to recommend an approach for upgrading the application.  What should you recommend？（）

• A、 Deploy to the Production slot.  Test the application， and then perform a VIP swap.
• B、 Deploy to the Staging slot.  Test the application， and then perform a VIP swap.
• C、 Deploy to the Staging slot.  Test the application， and then perform a manual in-place upgrade to the Production slot.
• D、 Deploy to the Staging slotTest the application， and then perform an automatic in-place upgrade to the Production slot.