老托精选阅读100篇之Passage 6中的两个问题!

老托精选阅读100篇之Passage 6中的两个问题!
为什么在from（红色）之前要加个used?个人感觉直接用from已经形成“alkalis来自于玻璃制造时的远古遗物”,参照后后面蓝色的from.原文第一段：Potash is one of the two alkalis that were used fromremote antiquity in the making of glass,and from the early Middle Agesin the making of soap.为什么不选A?（马老师给的答案是D,我始终想不通.）因为文章最后一句已经明确指出南部软木资源是匮乏的.—the softwoods in the South proved to be poor sources of the substance.10.According to paragraph 5,the softwoods in the South posed which ofthe following problems for southern settles?(A) The softwoods were not very plentiful.(B) The softwoods could not be used to build houses.(C) The softwoods were not very marketable.(D) The softwoods were not very useful for making potash.