Question:
Which position did John R. Bass hold in Aug, 2018?

Context:
 John R. Bass holds the position of Under Secretary of State for Management from Dec, 2021 to Dec, 2022. 
 John R. Bass holds the position of United States Ambassador to Georgia from Oct, 2009 to Jul, 2012. 
 John R. Bass holds the position of United States Ambassador to Turkey from Oct, 2014 to Oct, 2017. 
 John R. Bass holds the position of United States Ambassador to Afghanistan from Dec, 2017 to Jan, 2020. 
 John R. Bass holds the position of Executive Secretary of the United States Department of State from Oct, 2012 to Jul, 2014.

Answer:
United States Ambassador to Afghanistan