According to the passage, it has long been believed that ______.
A.
people in poor countries scarcely know how to enjoy a high standard of living
B.
the world's resources being limited, the people in underdeveloped countries are bound to live a poor life
C.
most Americans know that the world's resources of many kinds are becoming scarce
D.
it is impossible for all the people in the world' to improve their living standard