How do I submit my guess?

I'm assuming that the trivia contest leader board percentages are the number of team members with the correct answers? Either that or we have 115% of our backers reporting....

This choice does rather make itself, providing you're familiar with the region and the period the various peoples considered by the ancient authors as Thracian were here, from roughly the 7th century BCE through into the first half of the 1st century CE. Herodotus, writing in the 5th century BCE, did suggest one of the outlying Thracian peoples lived by the banks of both sides of the River Ister (= Danube), towards the Black Sea coast, the Getai, however, while others were suggested as inland as far as the Strymon and Axios Rivers (= Rivers Struma & Vardar), so the "bounds" of the region were probably always rather loose. Not THAT loose though!