这体确实比较难;原文给了两个factor,即两种情况:
1。 Each species of moth has an optimal body temperature for effective flight, and when
air temperatures fall much below that temperature, the moths typically have to remain inactive on vegetation for extended periods, leaving them highly vulnerable to predators.条件1时说如果气温太低,moth就全部冻住,容易被捕食——就是说大moth和小moth在被冻住的时候,被捕食率是一样的!2。In general,
larger moths can fly faster than smaller ones and hence have a better chance of evading flying predators, but they also have higher optimal body temperatures,
条件2说如果气温适宜,moths能飞的话(没被冻住),大moth的飞行技巧更高,所以能有效避免被捕食——就是说气温高的话,那就是大moth的天下;因为小moth飞行起来更容易被捕食,在一个period内被捕食率很高,逐渐的就只剩下大moth。
选项1阐述了原文的一个事实;这个选项本身没有错,但是作逻辑时要选最优选项;比较下来,2说的结论确实是题目的真实心意;很漂亮的一个选项!
-- by 会员 gzpg (2010/4/22 7:50:03)
我觉得这么解释好像更好一点: