A.SELECT学号FROMscorescWHERE课程号='C1'AND学号IN(SELECT学号FROMscorescWHERE课程号='C5')
B.SELECT学号FROMscorescWHERE课程号='C1'AND学号=(SELECT学号FROMscorescWHERE课程号='C5')
C.SELECT学号FROMscorescWHERE课程号='C1'AND课程号='C5'
D.SELECT学号FROMscorescWHERE课程号='C1'OR'C5'