The correct answer is option 2, Mark Jefferson. Mark Jefferson is a geographer who is associated with the concept of "primate city". A primate city is a city that is disproportionately larger than other cities in a country or region, both in terms of population and economic activity.

Option 1, August Losch, is not related to the concept of primate city. Losch was an economist and author of the book "The Economics of Location", which focused on industrial location theory.

Option 3, Griffith Taylor, is also not related to the concept of primate city. He was a geographer who contributed to the field of human geography and was known for his work on polar regions.

Option 4, W. Christaller, is associated with the concept of central place theory, not primate city. Christaller`s central place theory explains the distribution and size of settlements in an area based on the functions they provide and the market areas they serve.

In conclusion, Mark Jefferson is the geographer related to the concept of primate city.