Concept:The underlined vowel sound in "part" is the long open back vowel /ɑː/.Explanation:The word "part" is pronounced /pɑːt/.Its vowel sound is the same as in "aunt", which is pronounced /ɑːnt/."cat" has /æ/, "shout" has /aʊ/, and "cane" has /eɪ/.Therefore, the correct option is the word that shares the /ɑː/ sound.Answer:D. aunt