TOEFL一道阅读题

TOEFL一道阅读题
原文
Some of the world’s finest stone architecture can be seen in the ruins of the ancient Inca city of Machu Picchu high in the eastern Andes Mountains of Peru.The doorways and windows are made possible by placing over the open spaces thick stone beams that support the weight from above.A structural invention had to be made before the physical limitations of stone could be overcome and new architectural forms could be created.That invention was the arch,a curved structure originally made of separate stone or brick segments.
Why dose the author include a description of how the “doorways and windows” of Machu Picchu were constructed?
To provide an illustration of the kind of construction that was required before arches were invented
原文是说A structural invention即arch 先被 made,然後construction才可以created.但答案却相反说 the kind of construction 先被made,然後才是arch被invented
怎麼这麼怪?
看清这裏A structural invention had to be made before the physical limitations of stone could be overcome and new architectural forms could be created.That invention was the arch,就是说A structural invention即arch 先被 made,然後construction才可以created