Which part of the united nations is most is most responsible for keeping peace and solving disputes between countries

That would be the Security Council, as the name implies they focus on security

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a. because the u.s. was the leading with the most technology, economy, etc. also was teamed with other allies witch boosted the economy and materials to improve technology and use it.

payments were made after the 1940s.

in the 1980s, a commission held investigations and made recommendations.