"Differences in income inequality between countries of similar income levels can primarily be attributed to:"

skills biased technical change

Explanation:

the options were missing, so I looked for them:

Skills biased technical change takes place when skilled workers are favored over unskilled ones. This happens because the country's productive system requires a lot of skilled workers.

Income inequality is not generally the result of how intelligent a society or a person is, but instead where they are or where you were born. Humans have the capability of learning and prospering, but no one can do it all by themselves.

For example, rich countries that base their economies on exporting raw materials like Qatar have a very high GDP per capita ($69,688), but around 70% of the country's wealth is held by 10% of the population. Actually, the remaining 90% can be considered poor and live under very bad conditions. But Qatar's economy is based solely on exporting oil, it barely produces anything else.

you're crazy if you think that someone is going to write a 500 word report for you.