【题目】 设SC表中记录成绩的列为：Grade，类型为int。若在查询成绩时，希望将成绩按‘优’、‘良’、‘中’、‘及格’和‘不及格’形式显示，正确的Case函数是（　　）。     

Case Grade
　When 90~100  THEN  ‘优’
　When 80~89  THEN  ‘良’
　When 70~79  THEN  ‘中’
　When 60~69  THEN  ‘及格’
　Else  ‘不及格’
End

Case
　When Grade  between 90 and 100  THEN  Grade = ‘优’
　When Grade  between 80 and 89  THEN  Grade = ‘良’
　When Grade  between 70 and 79  THEN  Grade = ‘中’
　When Grade  between 60 and 69  THEN  Grade = ‘及格’
　Else  Grade = ‘不及格’
End

Case
　When Grade  between 90 and 100  THEN  ‘优’
　When Grade  between 80 and 89  THEN  ‘良’
　When Grade  between 70 and 79  THEN  ‘中’
　When Grade  between 60 and 69  THEN  ‘及格’
　Else  ‘不及格’
End

Case Grade
　When 90~100  THEN Grade = ‘优’
　When 80~89  THEN Grade = ‘良’
　When 70~79  THEN Grade = ‘中’
　When 60~69  THEN Grade = ‘及格’
　Else  Grade = ‘不及格’
End