Concept:The sound /aʊ/ is a diphthong, as in “now” or “house”.Explanation:“Fraught” is pronounced /frɔːt/, so it has /ɔː/, not /aʊ/.“Plough” is pronounced /plaʊ/, which contains the exact sound /aʊ/.“Fracas” is said as /ˈfrækɑː/, so it does not have /aʊ/.“Bat” is pronounced /bæt/, using /æ/ instead of /aʊ/.Answer:B. plough