学生表student和成绩表score通过字段sid关联，查询学生表sname字段和成绩表sc字段，以下哪个正确

A、selecta.sname,b.scfromstudentaandscorebwheresid=sid;
B、selectsname,scfromstudentwheresidin(selectsidfromscore);
C、selectstudent.sname,score.scfromstudent,scorewherestudent.sid=score.sid;
D、selectsnamefromstudentaunionselectscfromscorebwherea.sid=b.sid