In his 1920 campaign for president, warren g. harding said the country needed a return to:

The correct answer is sequences of comparable events.

The kind of patterns that historians look as they track differences in societies are sequences of comparable events.

When doing research on differences in societies, historians have to look for patterns in the societies they are studying to try to find sequences of comparable events. They need to compare similar variables in the societies they are comparing in order to have an accurate and valid comparison on circumstances, dates, and events.  

The other options of the question were, b) sequences of events that have nothing to do with each other, c) sequence of colors, and d) the order in which events occurred.