设有关系模式：student(sno, sname, age, dept)，现利用命令：CREATE VIEW stu AS SELECT *FROM student WHERE dept= cs WITH CHECK OPTION创建了一个视图。则以下SQl命令中能正确执行的是
A．UPDATE stu SET dept="maths"
B．UPDATE stu SET dept="maths"WHERE age＞=20
C．INSERT INTO stu VALUES ("2004001", "John", 30, "cs")
D．INSERT INTO stu VALUES ("2004001", "John", 50, "maths")