Question: What chemical phenomenon starts with the letter "c"?
Paraphrase: What chemical marvel begins with the letter "c"?
SPARQL (Wikidata): SELECT DISTINCT ?sbj ?sbj_label WHERE { ?sbj wdt:P31 wd:Q3382117 . ?sbj rdfs:label ?sbj_label . FILTER(STRSTARTS(lcase(?sbj_label), 'c')) . FILTER (lang(?sbj_label) = 'en') } LIMIT 25 
Answer: corrosion, corrosion