Let's identify which word in each set has an underlined part pronounced differently.

1. **A. lamps** (pronounced /æmps/)
**B. sinks** (pronounced /sɪŋks/)
**C. sofas** (pronounced /ˈsoʊ.fəz/)
**D. (not provided)**

Words A, B, and C share similar vowel sounds in their syllables, while "sofas" has a different vowel sound. So, **the answer is C. sofas**.

2. **A. full** (pronounced /fʊl/)
**B. lunch** (pronounced /lʌnʧ/)
**C. sun** (pronounced /sʌn/)
**D. study** (pronounced /ˈstʌdi/)

In this case, words B, C, and D share the same vowel sound /ʌ/, while "full" contains a different vowel sound /ʊ/. So, **the answer is A. full**.

3. **A. brother** (pronounced /ˈbrʌðər/)
**B. homework** (pronounced /ˈhoʊm.wɜrk/)
**C. mother** (pronounced /ˈmʌðər/)
**D. son** (pronounced /sʌn/)

Here, A, C, and D share the vowel /ʌ/, while "homework" contains a different vowel sound /oʊ/. So, **the answer is B. homework**.

4. **A. cat** (pronounced /kæt/)
**B. father** (pronounced /ˈfɑːðər/)
**C. calm** (pronounced /kɑːm/)
**D. family** (pronounced /ˈfæm.ɪ.li/)

In this set, words A and D share the vowel sound /æ/, while both B and C contain a different vowel sound /ɑ/. However, "father" and "calm" have the same /ɑː/ sound. So, **the answer is A. cat**.

To summarize:
1. C. sofas
2. A. full
3. B. homework
4. A. cat