Finding common themes and separating similar time periods from different time periods in history is known as select the best answer from the choices provided. secularization causation the renaissance periodization.

Periodization.

First of all, it sounds like it would make sense:  periodization sounds like a word that would describe splitting something into periods.  Also, the other answer choices don't make sense; secularization is the shift from religious beliefs to secular (less religious) ideals, causation is the relationship between cause and effect, and the Renaissance is just, well, the Renaissance (a period in history).