在SQL Server中，以下哪项是删除带有PRIMARY KEY约束的聚集索引的有效代码？( )
ALTER TABLE Production.ProductCost DROP CONSTRAINT PK_Product WITH (ONLINE = ON) GO
ALTER TABLE Production.ProductCostHistory DROP CONSTRAINT PK_Product DROP INDEX Index_Product WITH (ONLINE = ON) GO
DROP INDEX Index_Product ON Production.ProductCost GO
