What is the most effective way to combine sentences?

The byzantine empire weakened after asia minor

After nine states had ratified the constitution by mid-1788, other states quickly followed. all thirteen states had to obey it. it became law in the united states. none of the states had to obey it.

Ahistorian has discovered a letter written by an early roman emperor. she translates the letter and discovers that it contains orders to a general before a battle. she works to determine when the letter was written to figure out which battle the letter references.the historian in the passage is most clearly demonstrating which historical thinking skill? a. identifying causes and historical contextb. thinking chronologicallyc. making and evaluating arguments and interpretationsd. analyzing historical sources