8.25 综合 TPO 23
The lecture talks about reasons why three hypotheses stated in the reading passage to explain the decline of populations of the yellow cedar are not adequate. According to the lecture, the reasons are stated as follows.
First of all, the lecture indicates that
the yellow cedar are much more resistant than other kinds of trees to insect parasites. For example, they can release a kind of chemicals which is toxic. So the healthy
yellow cedar are unlikely to suffer from
beetle(是不是有点单复数部分?). And if some
yellow cedar are damaged by
beetle, they are probably going to die originally because of its unhealth rather than the reason of
beetle mentioned in the reading passage.
When it comes to the reason of brown bears listed in the reading passage, the lecture argues that while
the yellow cedar exist all across
the(国家前面不能加冠词) America, including mainland and island, bears don’t live in island. However, both the populations of the yellow cedar in mainland and island decrease
(这里both..and..的并列用这种顺序虽然能理解但是有点歧义,用the populations of yellow cedars in both mainland and island...是不是更明朗点?), thus it cannot be the bears that lead to the decline.
Last but not the least, the lecture suggests that the third hypothesis that it is because the affected roots system of the yellow cedar that result in the decline is not convincing, either. According to the lecture, if
it(这个it应该不是形式主语吧指代什么?) should blame the low temperatures, more
yellow cedar living in high elevations where temperature is lower than low elevations should die; however, the truth is that more yellow cedar in the low elevations die. Therefore, the last hypothesis said in the reading passage is disputed.
-- by 会员 ykhjy (2012/8/25 14:57:21)