Answer: C) study written records
Step-by-step explanation: A historian is the person who is expert in the field of history and works for gathering the historical information, analyzing , checking the authenticity along with the significance to study about that particular periods, geographical ethics, past phenomena etc.
They are most likely to study the data written in the form of records .Other options are incorrect because analyzing the artifacts and travelling are not the necessary and actual steps to be taken by historian.