单选题：设在SQL Server 2008某数据库中有表SC(Sn0，Cn0，Grade)，其中Grade列的类型为int。若在

设在SQL Server 2008某数据库中有表SC(Sn0，Cn0，Grade)，其中Grade列的类型为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，则下列Case函数中正确的是（　　）。 A．Case Grade
When Grade between 90 and 100 THEN Grade=ˊ优ˊ
When Grade between 80 and 89 THEN Grade=ˊ良ˊ
When Grade between 70 and 79 THEN Grade=ˊ由ˊ
When Grade between 60 and 69 THEN Grade=ˊ及格ˊ
Else Grade=ˊ不及格ˊ
End
A．Case Grade
When Grade between 90 and 100 THEN Grade=ˊ优ˊ
When Grade between 80 and 89 THEN Grade=ˊ良ˊ
When Grade between 70 and 79 THEN Grade=ˊ中ˊ
When Grade between 60 and 69 THEN Grade=ˊ及格ˊ
Else Grade=ˊ不及格ˊ
End
B．Case Grade
When Grade between 90 and 100 THEN ˊ优ˊ
When Grade between 80 and 89 THEN ˊ良ˊ
When Grade between 70 and 79 THENˊ中ˊ
When Grade between 60 and 69 THENˊ及格ˊ
Elseˊ不及格ˊ
End
B．Case Grade
When Grade between 90 and 100 THENˊ 优ˊ
When Grade between 80 and 89 THEN ˊ良ˊ
When Grade between 70 and 79 THEN ˊ中ˊ
When Grade between 60 and 69 THENˊ 及格ˊ
Elseˊ不及格ˊ
End
C．Case
When Grade between 90 and 100 THEN Grade=ˊ优ˊ
When Grade between 80 and 89 THEN Grade=ˊ良ˊ
When Grade between 70 and 79 THEN Grade=ˊ由ˊ
When Grade between 60 and 69 THEN Grade=ˊ及格ˊ
Else Grade=ˊ不及格ˊ
End
C．Case
When Grade between 90 and 100 THEN Grade=ˊ优ˊ
When Grade between 80 and 89 THEN Grade=ˊ良ˊ
When Grade between 70 and 79 THEN Grade=中ˊ
When Grade between 60 and 69 THEN Grade=ˊ及格ˊ
Else Grade=ˊ不及格ˊ
End
D．Case
When Grade between 90 and 100 THENˊ优ˊ
When Grade between 80 and 89 THEN ˊ良ˊ
When Grade between 70 and 79 THEN ˊ由ˊ
When Grade between 60 and 69 THEN ˊ及格ˊ
Elseˊ不及格ˊ
End

D．Case
When Grade between 90 and 100 THENˊ 优ˊ
When Grade between 80 and 89 THENˊ 良ˊ
When Grade between 70 and 79 THEN 中ˊ
When Grade between 60 and 69 THEN 及格ˊ
Elseˊ不及格ˊ
End