Question: Tell me which structural class of chemical compounds start with the letter u.
Paraphrase: Let me know which auxiliary lesson of chemical compounds begin with the letter u.
SPARQL (Wikidata): SELECT DISTINCT ?sbj ?sbj_label WHERE { ?sbj wdt:P31 wd:Q47154513 . ?sbj rdfs:label ?sbj_label . FILTER(STRSTARTS(lcase(?sbj_label), 'u')) . FILTER (lang(?sbj_label) = 'en') } LIMIT 25 
Answer: uronic acid, uronic acid, unsaturated hydrocarbon, unsaturated hydrocarbon, unsaturated compound, unsaturated compound, unsaturated fatty acids, unsaturated fatty acids, uranate, uranate, UDP-sugar, UDP-sugar, urate, urate, uranium compound, uranium compound, ultralow-molecular-weight heparin, ultralow-molecular-weight heparin, unsymmetrical ether, unsymmetrical ether, uranyl compound, uranyl compound, ulonic acid, ulonic acid