Sure! Here are the answers to both sections:

I) Choose the word A, B, C or D whose underlined part is pronounced differently:
1. **C**. teenage (the "-ea-" is pronounced as /iː/)
2. **C**. bread (the "ea" is pronounced as /ɛ/)
3. **A**. organize (the "o" is pronounced differently as /ɔː/)
4. **D**. these (the "th" is pronounced as /ð/)
5. **A**. eraser (the "e" is pronounced differently as /ɪ/)

II) Choose the word A, B, C or D whose main stress is different:
6. **C**. arrive (stress on the second syllable /əˈraɪv/)
7. **B**. power (stress on the first syllable /ˈpaʊər/)
8. **D**. visit (stress on the first syllable /ˈvɪzɪt/)
9. **C**. unluckily (stress on the second syllable /ʌnˈlʌkɪli/)
10. **D**. product (stress on the first syllable /ˈprɒdʌkt/)

These selections indicate which words have different pronunciations of the underlined parts or different main stress patterns.