Passage 2
      Human migration is the permanent change of   26   by an individual or group; it excludes
movements such as nomadism, migrant labor, commuting, and tourism, all of which are transitory
in nature. Migrations fall into several broad   27   . First, internal and international migrations
may be distinguishable. Within any country there are movements of individuals and families from
one area to another (for example, from rural areas to the cities), and this is   28   movements
from one country to another. Migrating to a new country is more complicated. Second, migration
may be voluntary or forced. Most voluntary migration, internal or external, is undertaken   29  
better economic opportunities or housing. Forced migrations usually involve people who   30  
by governments during war or other political upheavals or who have been forcibly transported as
slaves or prisoners. Intermediate between these two types of migrations are the voluntary
migrations of refugees fleeing from war, famine, or natural disasters.

【題組】26.
(A) residence
(B) habit
(C) shutter
(D) oppression