What is the correct order of steps for upgrading a cisco wcs？（）

A、back up the database， stop the wcs， upgrade the wcs， restore the database， start the wcs 

B、stop the wcs， back up the database， upgrade the wcs， restore the database， start the wcs

C、back up the database， stop the wcs， upgrade the wcs， start the wcs， restore the database 

D、stop the wcs， back up the database， upgrade the wcs， start the wcs， restore the database