The developing countries are dependent on cash crops – sugar, coffee, cacao, cotton.
Precipitating/violent/unexpected factors are those which reduce the food supply (droughts, floods, wars, epidemics)…
在段落浏览时,读者在看到信号词后,应不断对下文信息作出相应的判断,例如:
The main reason for (提示:下文信息重要) the reduction in the death rate in the developing world has been improved public health measures. For example, (提示:下文信息不重要,仅仅是为了用来证明前面的观点) in Sri Lanka the death rate was halved over ten years by spraying the mosquitoes which carry malaria. Why (提示:问题的答案中有读者应该关注的重点) is it so easy to cut the death rate in this way and yet so hard to reduce the birth rate? One answer (提示:这只是众多答案中的一种,并不是最重要的。) is that public health measures can be very cheap. Anti-malarial spraying is inexpensive. But this is not the important point (提示:but后面的是非常重要的信息). For birth control programmes to be successful, a change in attitude is required, whereas death control can be achieved autonomously. In other words, (提示:这里是作者想要强调的重要信息) the death rate can be cut without anything else changing.