(1) A prosperity which / that had never been seen before app

(1) A prosperity which / that had never been seen before appears in the countryside.农村出现了前所未有的繁荣.（which / that在句中作主语）
(2) The package (which / that) you are carrying is about to come unwrapped.你拿那个包裹快要散开了.(which / that在句中作宾语）
再如：
He drives a car that can travel 150 miles an hour.（作主语）
The car that he drives can travel 150 miles an hour.（作宾语）
如何判断定语从句是主语还是宾语?难以理解唉~求救~

只要看which or that 所指代的先行词在句子中做什么成分.
A prosperity which / that had never been seen before appears in the countryside.（which / that）指代的内容是A prosperity在定语从句A prosperity which / that had never been seen before中作主语.即
A prosperity had never been seen before.
a car （that） can travel 150 miles an hour.（作主语）
The car that he drives can travel 150 miles an hour.
{The car can travel 150 miles an hour.这是主句部分.}
拿着the car 往后面定语从句部分（he drives）去放,应放在 he drives 后..也就是做drive 的宾语.