What are the two main types of sources that a historian uses?

The two main types of sources are present sources (people their at the time) and post sources (overviews of what happened at the time) I am pretty sure this is correct

the correct answer is ) possibility.

demonstrating opportunity cost is done through production possibility.

the opportunity cost can be demonstrated using the production possibility frontier or curve. this graphic shows the total number of possibilities for two products when we have the resources needed and used in an efficient manner. the main resources could be money, labor, and technology. the curve shows that the production of one good increases when the production of the othe

answer; migrate from a region;