It,that与this的区别如下面这句话Some people have won two prizes , but t

This一般用于近指,一般是补充上一句的句子,或者说明一种情况和一种事物,就用This,This是These的单数形式,有时This和The比较难选择.
eg:Air flight would delay due to the bad weather,this is commonly seen.
That一般用于远指,定语从句,状语从句等等从句需要用That来联接.
eg:We have a hope that people landed in Malaysia Airlines Flight MH370 still be alive and will come back safely
It一般指动物罗,有时同位语从句一般用It开头
eg:It is a faith/wish/belief /(the way) that.

强调的重点不一样，题主给的例句中，语境强调【这种情况】很少见，所以用this更好而不用it或that。

that 主要用于远距离的事物。
this 主要用于近距离的事物。
it 主要指第三人称的“它”。