The correct answer to this open question is the following.
Although there are no options attached, we can say the following.
A book called "The Histories" uses research to determine the causes of the Greco-Persian Wars. It was written by the ancient Greek historian Herodotus around 440 BCE. It is a primary source because historian Herodotus was born in 485 BCE, in the Greek city of Halicarnassus, in a time were the Persians had invaded that place and was ruled by Lygdamis, a Persian governor. So Herodotus lived in the times of the Greco-Persian wars and witnessed some events of the war that started in 492BCE and ended in 448.
Primary sources include testimonies, scriptures, or information form witnesses or people who lived during the historical event. Secondary resources are the ones written by researchers that later wrote a book, journals, or encyclopedias.
