Question: Which country bordering the US once had a CO2 emissions per capita was metric ton?
Answer(s):
answer: Mexico

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.09c7w0)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.09c7w0 ns:location.location.adjoin_s ?y .
?y ns:location.adjoining_relationship.adjoins ?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 ?num .
}
ORDER BY DESC(?num) LIMIT 1