Sure! Let's look at the words and identify the one that has a different sound in the underlined part for each set.

1. **a. l**I**ve** - /lɪv/
**b. w**I**de** - /waɪd/
**c. b**I**cycle** - /ˈbaɪsɪkl/
**d. exc**I**ting** - /ɪkˈsaɪtɪŋ/
**Different sound: a. lIve** (short 'i' sound)

2. **a. f**EE**t** - /fiːt/
**b. s**E**At** - /siːt/
**c. n**E**Ar** - /nɪr/
**d. t**E**Am** - /tiːm/
**Different sound: c. nEAr** (short 'e' sound)

3. **a. b**Usy** - /ˈbɪzi/
**b. c**I**ty** - /ˈsɪti/
**c. th**I**nk** - /θɪŋk/
**d. terr**I**ble** - /ˈtɛrɪbl/
**Different sound: a. bUsy** (different vowel sound)

4. **a. gr**E**at** - /ɡreɪt/
**b. h**E**at** - /hiːt/
**c. ch**EA**k** - /tʃiːk/
**d. p**EA**ceful** - /ˈpiːsfəl/
**Different sound: c. chEAk** (different vowel sound)

5. **a. h**I**storic** - /hɪˈstɔːrɪk/
**b. exp**E**nsive** - /ɪkˈspɛnsɪv/
**c. off**I**ce** - /ˈɔːfɪs/
**d. f**I**nally** - /ˈfaɪnəli/
**Different sound: a. hIstoric** (different vowel sound)

If you need the phonetic transcriptions or additional information, feel free to ask!