TPO 3 reading architecture - 英檢

In order for the structure to achieve the size and strength necessary to meet
its purpose, architecture employes method of support that, because they are
basic on physical laws, have changed little since people first discovered
them-even while building materials have changed dramatically.

可以請教大家我跟怎麼去看這一串句子嗎?我不知道是我的TPO題庫有漏字，
還是原句就是如此？
我先說我覺得怪的點：
purpose到底是指什麼?support that是指purpose還是structure?
,have changed little~~~這個主詞到底是在說誰?是structure嗎?還是laws?
再來為什麼even前面會有個破折號
哀哀哀~麻煩大家解惑了！感激不盡




P.s.我預計五月二十五日要在台大考，2011年曾經考過一個78分，今年目
標希望能進步個十分阿~~誠徵一起奮發向上的朋友~有嗎有嗎?

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