若要使所有学科80分以上的成绩都增加5%，80至60分的成绩都增加10%，应如何更新数据库( )
A．UPDATE SC SET GRADE=GRADE*1.05 WHERE SC．GRADE>=80 UPDATE SC SET GRADE=GRADE*1.10 WHERE SC．GRADE>=60 AND SC．GRADE<=80
B．UPDAIE SC SET GRADE=GRADE*1.10 WHERE SC．GRADE>=60 AND SC．GRADE<=80 UPDATE SC SET GR ADE=GRADE* 1.05 WHERE SC．GRADE>=80
C．UPDArE SC SET GRADE=GRADE*1.05 WHERE SC．GRADE>=80 AND SET GRADE =GRADE*1.10 WHERE SC．GRADE>=60
D．UPDATE SC SET GRADE=GRADE*1.10 WHERE SC．GRADE>=60 AND SC．GRADE <=80 AND SET GRADE=GRADE*1.05 WHERE SC．GRADE>=80