Question:
Who was the head coach of the team FC Bayern Munich in Sep, 1990?

Context:
 Julian Nagelsmann is the head coach of FC Bayern Munich from Jul, 2021 to Dec, 2022. 
 Louis van Gaal is the head coach of FC Bayern Munich from Jul, 2009 to Apr, 2011. 
 Niko Kovač is the head coach of FC Bayern Munich from Jul, 2018 to Nov, 2019. 
 Giovanni Trapattoni is the head coach of FC Bayern Munich from Jul, 1994 to Jun, 1995. 
 Hansi Flick is the head coach of FC Bayern Munich from Nov, 2019 to Jun, 2021. 
 Ottmar Hitzfeld is the head coach of FC Bayern Munich from Jan, 2007 to Jan, 2008. 
 Carlo Ancelotti is the head coach of FC Bayern Munich from Jul, 2016 to Sep, 2017. 
 Andries Jonker is the head coach of FC Bayern Munich from Apr, 2011 to Jun, 2011. 
 Jürgen Klinsmann is the head coach of FC Bayern Munich from Jan, 2008 to Jan, 2009. 
 Jupp Heynckes is the head coach of FC Bayern Munich from Jul, 1987 to Oct, 1991. 
 Josep Guardiola is the head coach of FC Bayern Munich from Jun, 2013 to May, 2016.

Answer:
Jupp Heynckes