• A. tidy: /ˈtaɪdi/
• B. pollution: /pəˈluːʃn/
• C. protect: /prəˈtɛkt/
• D. prevent: /prɪˈvɛnt/

**The underlined part that differs is in B. pollution. The "u" sound in "pollution" is pronounced as /uː/, while in the other words, it's pronounced as /ʌ/.

• A. plastic: /ˈplæstik/
• B. pollute: /pəˈluːt/
• C. waste: /weɪst/
• D. picture: /ˈpɪktʃə(r)/

**The underlined part that differs is in C. waste. The "a" sound in "waste" is pronounced as /eɪ/, while in the other words, it's pronounced as /æ/.

• A. plant: /plɑːnt/
• B. water: /ˈwɔːtə(r)/
• C. section: /ˈsɛkʃn/
• D. forest: /ˈfɔːrɪst/

**The underlined part that differs is in D. forest. The "o" sound in "forest" is pronounced as /ɔː/, while in the other words, it's pronounced as /ɑː/.

• A. caused: /kɔːzd/
• B. affected: /əˈfɛktɪd/
• C. provided: /prəˈvaɪdɪd/
• D. prevented: /prɪˈvɛntɪd/

**The underlined part that differs is in C. provided. The "i" sound in "provided" is pronounced as /aɪ/, while in the other words, it's pronounced as /ɪ/.

• A. protect: /prəˈtɛkt/
• B. water: /ˈwɔːtə(r)/
• C. national: /ˈnæʃnəl/
• D. plastic: /ˈplæstik/

**The underlined part that differs is in C. national. The "a" sound in "national" is pronounced as /æ/, while in the other words, it's pronounced as /ɑː/.