Paragraph 3：In order for the structure to achieve the size and strength necessary to meet its purpose, architecture employs methods of support that, because they are based on physical laws, have changed little since people first discovered them-even while building materials have changed dramatically. The world’s architectural structures have also been devised in relation to the objective limitations of materials. Structures can be analyzed in terms of how they deal with downward forces created by gravity. They are designed to withstand the forces of compression (pushing together), tension (pulling apart), bending, or a combination of these in different parts of the structure.
3. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
○Unchanging physical laws have limited the size and strength of buildings that can be made with materials discovered long ago.
○Building materials have changed in order to increase architectural size and strength, but physical laws of structure have not changed.
○When people first started to build, the structural methods used to provide strength and size were inadequate because they were not based on physical laws.
○Unlike building materials, the methods of support used in architecture have not changed over time because they are based on physical laws.
答案选D，我选的B是哪里错了呢？
Paragraph 6: Much of the world’s great architecture has been constructed of stone because of its beauty, permanence, and availability. In the past, whole cities grew from the arduous task of cutting and piling stone upon. 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 That invention was the arch, a curved structure originally made of separate stone or brick segments. The arch was used by the early cultures of the Mediterranean area chiefly for underground drains, but it was the Romans who first developed and used the arch extensively in aboveground structures. Roman builders perfected the semicircular arch made of separate blocks of stone. As a method of spanning space, the arch can support greater weight than a horizontal beam. It works in compression to divert the weight above it out to the sides, where the weight is borne by the vertical elements on either side of the arch. The arch is among the many important structural breakthroughs that have characterized architecture throughout the centuries.
10. Why does the author include a description of how the “doorways and windows” of Machu Picchu were constructed?
○To indicate that the combined skeletons and skins of the stone buildings of Machu Picchu were similar to igloos and adobe structures
○To indicate the different kinds of stones that had to be cut to build Machu Picchu
○To provide an illustration of the kind of construction that was required before arches were invented
○To explain how ancient builders reduced the amount of time necessary to construct buildings from stone.
答案是C，楼主能帮我说明下答案得出的思路么？
谢谢
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