A:①→②→③→④
B:①→③→②→④
C:③→①→②→④
D:③→①→④→②
A: How did you go there?
B: I went spaceship. ( )
已知M,N为集合I的非空真子集,且M,N不相等,若N∩CIM=∅则M∪N=( )