单项选择题
A.select *from students where height is nullB.select *from students where height=nullC.select height is null from studentsD.select height=null from students
A.likeB.%C.inD.between...in...
A.select *from students order by age desc，height descB.select *from students order age asc，height descC.select *from students order by age desc，height ascD.select *from students order by age asc，height desc