[单项选择] Migration is usually defined as "permanent of sempermanent change of residence." This broad definition, of course, would include a move across the street or across a city. Our concern is with movement between nations, not with internal migration within nations, although such movements often exceed international movements in volume. Today, the motives of people who move short distances are very similar to those of international migrants. Students of human migration speak of" push" and" pull" factors, which influence all individual’’ s decision to move from one place to another. Push factors are associated with the place of origin. A push factor can be as simple and mild a matter as difficulty in finding a suitable job, or as traumatic as war, or severe famine. Obviously, refugees who leave their homes with guns pointed at their heads are motivated almost entirely by push factors (although pull factors do influence their choice of destination). Pull factors are those associate
A. Migration of large numbers of people may cause conflict.
B. The newest arrivals can hardly get good jobs.
C. Native people often resent newest arrivals because they cannot communicate easily with the latter.
D. Usually it has taken several decades for each group of newest arrivals to be accepted into the mainstream of society in the host country.