According to article 13 of the articles of confederation, what percentage of votes by the states was required to ratify any amendments?

Dr. robbins wants to know if there are different opinions regarding the value of public school education between native americans who have at least one relative who attended indian boarding school and native americans who have no family experience with indian boarding school. dr. robbins contacts 35 native american participants in each group. he wants each group to include younger as well as older adults, and a mix of male and female participants. he asks each person to complete a survey about their attitudes toward public education. the design of this study is:

How did ancient civilizations develope its agriculture and protect its population

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