A.
SELECT Cno FROM Course WHERE NOT Cpno=NULL AND Ccredit<4< /div>
B.
SELECT Cno FROM Course WHERE Cpno=NOT NULL AND Ccredit<4< /div>
C.
SELECT Cno FROM Course WHERE NOT Cpno IS NULL AND Ccredit<4< /div>
D.
SELECT Cno FROM Course WHERE Cpno<>NULL AND Ccredit<4< /div>