In the video form. the OrderDate field (Which shows When the video may be ordered)is calculated based on the Date field (Which displays the release date ). The order date is 30 days prior to  the release date. Which one the following formulas will calculate the OrderDate value?（）

• A、@Number(Date)-30       
• B、@Adjust(Date;0;0;30;0;0;0) 
• C、@Adjust(Date;0;0;-30;0;0;0) 
• D、@If(Date!="";Date-30;@Failure(There is no current release date"))