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发生的情形是每次某种资源好像要被用尽的时候，其价格就开始上涨。于是人们便作出响应，寻找新的资源供给，试图找到节省使用这种稀缺资源的办法或者寻找一种新的替代资源。
本句的主干是What has happened is that...。What has happened为主语从句，that引导的是表语从句that every time...new substitute；every time为该表语从句的时间状语，而a material seems to be running short则为省略关系副词when的定语从句修饰time the price has risen and，in response，people have...a new substitute为该表语从句的主干。
in response在句中作插入语，意为"作为回应；与之相应"。如：
In response，the restaurant began offering more seating.
作为回应，该餐厅开始提供更多的座位。
I have run short of money.
我正缺钱用。
She is seeking a substitute for the man who broke her heart.
她在寻觅一个人来替代那个伤了她的心的男人。
在句中作主语的从句叫主语从句，它可以直接放在句首作句子的主语，也可以放到句子的后部，前面用it作其形式主语。以上两种结构基本可以换用。但是，由what、whoever、whatever等引导的主语从句前一般不用形式主语it。如：
That he will come here on Tuesday is certain.他周二会来这里是确定的事实。可以改写成：It is certain that he will come here on Tuesday.
What he told me was true.他告诉我的是真的。不胄瓯兑：It was true what he told me.
