Khan Academy
Khan Academy: An Introduction to the Song Dynasty (960 1279)
The Song dynasty was the second great "medieval" period of China. Northern Song (while it lasted) and the Southern Song (from 1127 until 1279) achieved incredible feats of learning, science, art, and philosophy. International trade and...
Khan Academy
Khan Academy: Sufficient Assumptions Quick Guide
This question asks you to identify a sufficient assumption -- that is, an assumption that, if added to the argument, would make it logically valid. We're looking for something that would fix all of an argument's problems, bridging the...