What kind of source would a historian use to get a first hand account of a past event

Is the weather changing? consider the data of severe weather that includes tornadoes occurring throughout the u. s. over the last four years. compare the severe weather for the last three years. then compare the first three months of 2017 with that data. based on previous years, what might the prediction be for weather during 2017?

What was the mame given to the idea that americans should expand across the nation ro the pacific coast

Someone who accepted the beliefs of social darwinism would have also agreed with which of these statements?