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（　　）。
单选题 (3 分) 3分
A.
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

B.
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

C.
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

D.
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

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