新概念英语逐句解读3
A puma at large 逃遁的美洲狮 （第三册第1课）
3. However, as the evidence began to accumulate, experts from the Zoo felt obliged to investigate, for the descriptions given by people who claimed to have seen the puma were extraordinarily similar.
可是，随着证据越来越多，动物园的专家们感觉到有必要进行一番调查，因为凡是声称见到过美洲狮的人们所描述的情况竟是出奇地相似。
accumulate [əˈkju:mjəleɪt]（积累、积聚）means to gradually increase over a period of time.
We have accumulated a great amount of evidence.
我们已经积累了大量的证据。
feel obliged to sth：must, have to: 感到必须要做某事(经常用作书面语)。
I felt obliged to invite him to our wedding.
我觉得有必要邀请他参加我们的婚礼。
feel也有"有必要做某事，应该做某事"的意思。
I feel I should resign.
我觉得自己应该辞职。
oblige: （形势、法律）迫使，如蒙…将不胜感激
I would be obliged if you could attend our wedding.
您若能参加我们的婚礼，我将不胜感激。
这句话中用了as、for两个词来引出两个状语从句，我们先将其进行拆分：
主句：Experts from the Zoo felt obliged to investigate.
从句1：The evidence began to accumulate。
从句2：the descriptions given by people who claimed to have seen the puma were extraordinarily similar.
其中，从句2中的主句：the descriptions were extraordinarily similar. 使用了过去分词given作后置定语，后置定语嵌套了一个由who引导了一个定语从句修饰people。
我们来模仿写一句。
However, as it became hotter and hotter, we felt obliged to buy an air-conditioner, for the existing air conditioner doesn't work.
可是，随着天天越来越热，我们必须买一台空调，因为那台空调坏了。
