Question:
Who was the head of Mons in May, 2009?

Context:
 Abel Dubois is the head of the government of Mons from Jan, 1974 to Jan, 1989. 
 Leo Collard is the head of the government of Mons from Jan, 1972 to Jan, 1974. 
 Elio Di Rupo is the head of the government of Mons from Jan, 2001 to Dec, 2018. 
 Maurice Lafosse is the head of the government of Mons from Jan, 1989 to Jan, 2001.

Answer:
Elio Di Rupo