— Must I finish the work tonight?
— No, you . But you finish it tomorrow.
A:can't; need
B:mustn't; may
C:needn't; must
D:mustn't; can
①S△ODB=S△OCA;
②四边形OAMB的面积不变;
③当点A是MC的中点时,则点B是MD的中点.
其中正确结论的个数是( )