按照学生平均成绩（avg_grade）将students表中的数据检索出来，下面SQL语句正确的是（）

A、SELECT*FROM students ORDERBYavg_grade

B、SELECT*FROM students GROUPBYavg_grade ASC

C、SELECT*FROM students ORDERBYavg_grade DESC

D、SELECT*FROM students ORDERbyavg_gradeasc