this 有“这个”的意思,that 有“那个”的意思, “it”就是一个英语中的虚主语, 都指的是先前所提及的地方或者事情。 this "referring to the one nearer in place, time, or thought";
"That" indicate a person, thing, idea, state, event, time, remark, etc., as pointed out or present, mentioned before"
"it" is a dummy subject that is often understood by context.