To choose the word with the underlined part pronounced differently in each group, let's analyze the pronunciation of the underlined parts:

1. **A. receive** (pronounced /rɪˈsiːv/)
**B. staircase** (pronounced /ˈstɛərˌkeɪs/)
**C. communal** (pronounced /ˈkɒmjʊnəl/)
**D. culture** (pronounced /ˈkʌltʃər/)

The underlined part in "receive" is pronounced /iː/, while in the other words, the underlined parts are pronounced differently. So, the answer is **A. receive**.

2. **A. school** (pronounced /skuːl/)
**B. chemistry** (pronounced /ˈkɛmɪstri/)
**C. chaotic** (pronounced /keɪˈɒtɪk/)
**D. children** (pronounced /ˈtʃɪldrən/)

The underlined part in "chemistry" is pronounced /k/, while in the other words, the underlined parts are pronounced differently. So, the answer is **B. chemistry**.

3. **A. keep** (pronounced /kiːp/)
**B. know** (pronounced /noʊ/)
**C. kitchen** (pronounced /ˈkɪtʃɪn/)
**D. keen** (pronounced /kiːn/)

The underlined part in "know" is pronounced /n/, while in the other words, the underlined parts are pronounced /k/. So, the answer is **B. know**.

4. **A. guest** (pronounced /ɡɛst/)
**B. tiger** (pronounced /ˈtaɪɡər/)
**C. age** (pronounced /eɪdʒ/)
**D. gathering** (pronounced /ˈɡæðərɪŋ/)

The underlined part in "guest" is pronounced /ɡ/, while in the other words, the underlined parts are pronounced differently. So, the answer is **A. guest**.

5. **A. girl** (pronounced /ɡɜːrl/)
**B. village** (pronounced /ˈvɪlɪdʒ/)
**C. game** (pronounced /ɡeɪm/)
**D. garden** (pronounced /ˈɡɑːrdən/)

The underlined part in "village" is pronounced /v/, while in the other words, the underlined parts are pronounced /ɡ/. So, the answer is **B. village**.