Question: What West African countries once had CO2 emissions per capita  of 2009 metric ton?
Answer(s):
answer: Benin
answer: Burkina Faso
answer: Ghana
answer: Guinea
answer: Guinea-Bissau
answer: Liberia
answer: Mali
answer: Mauritania
answer: Nigeria
answer: Sierra Leone
answer: Senegal
answer: Togo
answer: Ivory Coast
answer: Gambia

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.0hqjh)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.0hqjh ns:location.location.contains ?x .
?x ns:common.topic.notable_types ns:m.01mp .
?x ns:location.statistical_region.co2_emissions_per_capita ?c .
?c ns:measurement_unit.dated_metric_ton.date "2009"^^xsd:dateTime . 
}