it和that指代的区别

题目

it和that指代的区别
the population of china is much larger than of japan 换成It哪里错
life is much easier than used to be 换成that 哪里错
life is much easier than (it) was in the 20 centry换成that 哪里错
ife is much easier than (that) in the 20 centry换成It哪里错
还有：同一个人或物,两个不同的时间进行对比时,应该用人称代词.两个不同的人、物、地点、天气等进行对比时,用that.这个对么

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