请教GWD4-14！

Guidebook writer:  I have visited hotels throughout the country and have noticed that in those built before 1930 the quality of the original carpentry work is generally superior to that in hotels built afterward.  Clearly carpenters working on hotels before 1930 typically worked with more skill, care, and effort than carpenters who have worked on hotels built subsequently.

A   The quality of original carpentry in hotels is generally far superior to the quality of original carpentry in other structures, such as houses and stores

B    Hotels built since 1930 can generally accommodate more guests than those built before 1930

C   The materials available to carpenters working before 1930 were not significantly different in quality from the materials available to carpenters working after 1930

D   The better the quality of original carpentry in a building, the less likely that building is to fall into disuse and be demolished

E    The average length of apprenticeship for carpenters has declined significantly
                                        since 1930

谁能告诉我为什么选D吗？

我的理解是A的比较扩大了讨论范围，B能容纳多少人跟质量好坏的结论无关，C说材料一样甚至间接的支持了文中观点，E对文中观点也是支持。D说质量越好，建筑物越不容易停止使用或毁坏，那么30年代前的建筑现在还在使用不是也是支持文中观点吗？怎么理解成削弱呢？？？

逻辑是软肋，多谢大家帮助了！

关键字在于in those built before 1930 the quality of the original carpentry work is GENERALLY superior to that in hotels built afterward. 由于1930年前的那些木工质量差的房子都被毁了，所以现存的1930年前的房子木工的整体质量就高了。

我现在什么都是软肋，呵呵，LZ加油！