English history is often divided into eras named after the king or queen who ruled over the country during that time. this is and example of which of the following?

a) determining bias
b) historiography
c) periodization
d) historical argument

C) Periodization

Periodization is a useful tool in studying history because it helps to divide the time periods into distinctive blocks of time. We can use this to reference the culture or distinctive movements in society at the time.
Many of the European periods are named after a significant ruler or a dominant family from that time period. This is why you may hear someone reference the "Victorian", "Tudor", or "Edwardian" era.