I would like to ask about the pronouns: That is what.. , This is what … , It’s what….. . which are used in the following.
  My question is:
  1. Are the following pronouns “That, this, it” same in meaning?
    I think they mean “Most ………..change.”  What do you think?
  2. The order in which they are used here is That, This, and It.
    I wonder why That comes first, not This.
    Is the order fixed?  That/This comes first and then It comes.