Concept:The word "heart" has the long vowel sound /ɑː/, and we must find the option that shares the same vowel sound.
Explanation:The given word "heart" is pronounced /hɑːt/.
Its underlined vowel sound is the long open back vowel /ɑː/.
Now check the pronunciation of each option.
A. "mark" is pronounced /mɑːk/, so it contains the same vowel sound /ɑː/.
B. "bag" is pronounced /bæɡ/, which has the vowel sound /æ/, not /ɑː/.
C. "anger" is pronounced /ˈæŋɡə/, which also has /æ/ as its vowel sound.
D. "carry" is pronounced /ˈkæri/, so it has /æ/ and does not match /ɑː/.
Only "mark" has the same vowel sound as "heart".
Answer:A. mark