关于归纳题的有关无关问题，还是困惑！附题一道。。

请教：感觉归纳题的信息应该都是根据文中所给，然后得到一个没有附加信息conclusion才对，也就是说归纳题应该可以直接用有关无关排除吧？

拿道题：145. Between 1975 and 1985, nursing-home occupancy rates averaged 87 percent of capacity,
while admission rates remained constant, at an average of 95 admissions per 1,000 beds per
year. Between 1985 and 1988, however, occupancy rates rose to an average of 92 percent of
capacity, while admission rates declined to 81 per 1,000 beds per year.

If the statements above are true, which of the following conclusions can be most properly
drawn?
(A) The average length of time nursing-home residents stayed in nursing homes increased
between 1985 and 1988.
(B) The proportion of older people living in nursing homes was greater in 1988 than in
1975.
(C) Nursing home admission rates tend to decline whenever occupancy rates rise.
(D) Nursing homes built prior to 1985 generally had fewer beds than did nursing homes
built between 1985 and 1988.
(E) The more beds a nursing home has, the higher its occupancy rate is likely to be.

答案是：（A）

可是The average length of time 这个概念是文中根本没有提到的，用有关无关排除，只能得到C相关。

我知道如果知道文章的意思就可以知道，但是问题是我通过查讨论贴知道很多人都不明白这道题的意思，尤其是nursing-home occupancy rates 和 admission rates 的意思，那在实考时很难用推理出来呀？？请问各位CDer是怎么看这道题的呢，对于这种归纳题是怎么看待无关问题呢？？

期待各位的不吝赐教咯~~

我的理解：

conclusion有两类：充分条件类，即A导致B，B导致C,可以推出A导致C，是一种“顺畅”的推理；

                  必要条件类：这其实等于assumption.

至于有关无关，却是应该是不能出现新内容，但是新内容并不是说只要这个词在原文中没有出现，就是新内容，应该要注意新内容和相关内容的区分。比如说这个题，讨论的是nursing-home occupancy, capacity, admission rates,三者的关系。A选项中的average of length of time貌似无关，其实是与三者相关的。