Question:
Which position did Dietmar Keller hold in Sep, 1989?

Context:
 Dietmar Keller holds the position of member of the German Bundestag from Dec, 1990 to Nov, 1994. 
 Dietmar Keller holds the position of member of the Volkskammer from Mar, 1990 to Oct, 1990. 
 Dietmar Keller holds the position of minister from Jan, 1989 to Jan, 1990.

Answer:
minister