D. recipes (s)
(The others end with a /s/ sound, while "recipes" ends with a /z/ sound.)

D. roofs (s)
(The others end with a /s/ sound, while "roofs" ends with a /z/ sound.)

C. gym
(The others have a vowel sound that is pronounced differently; "gym" has a short /ɪ/ sound.)

D. handball
(The stress pattern is different; "hobby," "hockey," and "chat" are one-syllable words.)

C. competition
(The others have the main stress on the second syllable, while "competition" has stress on the third syllable.)

C. practice
(The others have the main stress on the first syllable, while "practice" has the stress on the second syllable.)

D. prefer
(The others have the stress on the second syllable, while "prefer" has the stress on the second syllable as well but it’s different.)

D. music
(The others have two syllables with the stress on the first syllable, while "music" is pronounced with stress on the first syllable but is a different word.)

A. machine
(The others have stress on the first syllable, while "machine" has stress on the second syllable.)