Pull factors leading to immigration include job opportunities, political and religious freedom, access to education, and the prospect of a better life for oneś children.

In the 20th Century these pull factors have encouraged migration primarily...

a
from less-developed (poor) countries to more-developed countries.
b
among people with similar religious beleifs.
c
among people with similar eating habits
d
from more developed (rich) countries to less developed (poor) countries

A is correct because during the 20th century, with the migration policies being made much more friendly and open, the people from the less-developed countries where the living conditions were terrible, to the more-developed countries where they could have much better lives.

B is not correct because it is actually the opposite, where people from different religious beliefs than those of the people of the county of their choice, have migrated and made much more diverse societies.

C is not correct because such migration has not been recorded so far.

D is not correct because the people from more-developed countries usually only visit the less-developed countries as tourists, but very very rarely migrate to them as they are aware of the risks and bad living conditions.