Question: Which isotope of bismuth has the longest half-life?
Paraphrase: Which bismuth isotope has the longest rate of decay?
SPARQL (Wikidata): select ?ent where { ?ent wdt:P31 wd:Q1372372 . ?ent wdt:P2114 ?obj } ORDER BY DESC(?obj)LIMIT 5 
Answer: bismuth-209, bismuth-210m, bismuth-208, bismuth-189, bismuth-196