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What is the main difference between primary and secondary sources? a. primary sources are historical documents, and secondary sources are modern-day documents. b. primary sources are derived from museums and archives, and secondary sources are created by history students and academics. c. primary sources are found in ancient places with a rich history, and secondary sources are found in historical journals and blogs. d. primary sources are created during a particular historical era, and secondary sources are created by studying primary sources.

Search america's open door policy with china beginning in 1899. explain how relations with the united states and china have changed and the effects of the open door policy on both countries.

What was one important characteristic of the russian military during world war i? a. it had more advanced military technology than its western european allies. b. it was an all-volunteer military that enjoyed high morale throughout the war. c. it defended russian territory but refused to attack german positions d. it was unable to provide its forces with adequate weapons and supplies.