Question: What is the isotope of neutronium with the lowest average lifetime that is a subclass of neutronium?
Paraphrase: What isotope and subclass of neutronium has the lowest average lifetime?
SPARQL (Wikidata): select ?ent where { ?ent wdt:P31 wd:Q12525553 . ?ent wdt:P2645 ?obj . ?ent wdt:P279 wd:Q1195471} ORDER BY ASC(?obj)LIMIT 5 
Answer: neutron