A.
s tudent [ ] s = new s tudent [ 2 ]; s [ 0 ]=new s tudent ("李四",21); s [ 1 ]= s [ 0 ] ;
B.
s tudent [ ] s = new s tudent [ 2 ]; s tudent s [ 0 ]=new s tudent ("李四",21); s [ 1 ]= s [ 0 ] ;
C.
s tudent [ 2 ] s = new s tudent []; s [ 0 ]=new s tudent ("李四",21); s [ 1 ]= null;
D.
s tudent s = new s tudent []; s [ 0 ]=new s tudent ("李四",21); s [ 1 ]= null;