根据下面材料，回答第 31～35 题：

第 31 题 We can infer from the first paragraph that _______.（　　）

[A] the past central operating assumption conforms to the present condition

[B] the poor in middle-income countries have outnumbered those in Africa

[C] most of the impoverished "bottom billion" have emigrated from Africa

[D] the poor in middle-income countries are quite odd in behavior.