【单选题】与查询Select student.* from student,grade Where student.sno=grade.sno and grade.score>90等价的语句是()。
A、Select * from student Where exists (select sno from grade where score>90)
B、Select * from student Where sno exists (select sno from grade where score>90)
C、Select student.* from student,grade Where grade.score>90
D、Select * from student Where sno in (select sno from grade where score>90)