细节1, in part because the viruses themselves follow an infectious cycle in which, if protected from direct sunlight, they may remain virulent for many years
细节1,but population ecologists had usually considered viral disease to have contributed to the decline once it was underway rather than to have initiated it
是类比推理,做题的时候判断成相关因果推理了,之前有个类似的题目,说的是账单上有银联标志的得到的消费多。。那是什么推理来着。。