成绩表SCInfo（StId，CNo，Score）的属性StId表示学号，CNo为课程编号，Score为成绩。从SCInfo表中找出无成绩的元组的SQL语句是（）。

A.SELECT *FROM SCInfo WHERE Score=NULL
B.SELECT*FROM SCInfo WHERE Score IS "
C.SELECT*FROM SCInfo WHERE Score ="
D.SELECT *FROM SCInfo WHERE Score IS NULL