求助一下GWD-4-14~

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.

Which of the following, if true, most seriously weakens the guidebook writer’s argument?

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. 后面这句是啥米意思？为什么这个现象在文中都没提过的会能够起到削弱作用

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

说实话最初我选的是B，虽然觉得关系不大但是是用排除法排除出来的，笨笨我实在是脑子糊掉搞不清为什么D能削弱了。。请各位大大们帮忙解决下~感激不尽s~

thx for the help! I am confused about it for a long time.