下面选项中,用于将表student中字段grade值更新为80的SQL语句是 A: ALTERTABLEstudentsetgrade=80; B: UPDATEstudentsetgrade=80wheregrade=80; C: UPDATEstudentsetgrade=80wheregrade<=80; D: UPDATEstudentsetgrade=80;

下面选项中,能够更新表student中id值小于4的SQL语句是 A: ALTERTABLEstudentwhereid<4; B: UPDATEstudentsetgrade=100whereid<4; C: UPDATEstudentsetgrade=100whereid<=4; D: UPDATETablestudentsetgrade=100whereid<4;