What is an example of a primary source?

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 a. primary sources are historical documents, and secondary sources are modern-day documents.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.

Use the map of russia to answer the follow question: ships could reach the port of st. petersburg via the baltic sea. where is that sea?

Which colony leader urged virginia's to prepare for war