Question: Which is the region of Belgium that had Dutch as official language?
Paraphrase: Which is the locale of Belgium that had Dutch as official language?
SPARQL (Wikidata):  select distinct ?sbj where { ?sbj wdt:P37 wd:Q7411 . ?sbj wdt:P31 wd:Q83057 } 
Answer: Flemish Region, Flanders, Brussels