The World Distribution of Income Has Become More Equal Since

The world distribution of income has become more equal since 1970 because

A) average incomes in poorer countries are rising much faster than average incomes in rich countries.
B) the distribution of income within most countries has become more equal.
C) foreign aid programs from rich nations have increased in size and especially in effectiveness.
D) technology is used similarly in all countries.
E) the world population is increasing.