假设v1是基于SC表产生的视图,定义如下:create view v1 AS select sno, avg(score) from sc group by sno;则下面对视图的操作语句()是能正确执行的?I. update v1 set avg(score)=90 where sno='18010502001';II. select * from v1 where sno='18010502001'; A.
仅I B.
仅II C.
I和II都能 D.
I和II都不能