进行索引优化时候，下面SQL遵循了“独立列原则”的是？
A.SELECT studentNo,studentName, sex FROM student WHERE studentNo+1= 5;
B.SELECT * FROM student WHERE substring(studentName,1,1)= "黄";
C.SELECT studentNo,studentName, sex FROM student WHERE studentNo= 5-1;
D.以上都没有遵循
正确答案是C