边际进口倾向是指（）增加在（）增加中所占的比例。
参考答案：进口；国内生产总值
There are several landladies approved by the universities who take in _____.
A．lodgers
B．residents
C．inhabitants
D．settlers
简述从顾客需求角度划分，一般可分为哪几类。
