Please help me match US presidents to the events

Which of the following best describes the relationship between the united states and south korea today?

What is the main social system that existed in ancient china?

Historians have recently discovered a historical journal published in the early twentieth century. the journal contains facts based on original sources about the downfall of the early byzantium empire. historians consider this long-lost journal to be a breakthrough in their understanding of the byzantium empire. based on this information, the journal is a source.