What was Gan De's contribution to astronomy? O A.
He developed the world's first star catalogue.
B.
He was the first to record a lunar eclipse.
OC.
He was the first to observe planets.
D.
He invented the telescope

Which of the following flow charts accurately illustrates the history of constitutional amendments in the united states?

What is the main idea of this excerpt

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 a. primary sources are historical documents, and secondary sources are modern-day documents.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