Let's go through each exercise and identify the correct answers:

**Exercise 1: Choose the words whose underlined part is pronounced differently from that of the others in each group.**

1. A. chef
B. choose
C. cheese
D. watch

- Answer: A. chef (The "ch" in "chef" is pronounced /ʃ/, while in "choose" and "cheese" it is pronounced /tʃ/.)

2. A. picks
B. laughs
C. facilities
D. ropes

- Answer: B. laughs (The "s" in "laughs" is pronounced /s/, while in "picks," "facilities," and "ropes" it is pronounced /z/.)

3. A. peace
B. meat
C. bread
D. beach

- Answer: C. bread (The "ea" in "bread" is pronounced /ɛ/, while in "peace," "meat," and "beach" it is pronounced /iː/.)

4. A. folk
B. rope
C. top
D. home

- Answer: C. top (The "o" in "top" is pronounced /ɒ/, while in "folk," "rope," and "home" it is pronounced /oʊ/.)

5. A. send
B. herb
C. sell
D. send

- Answer: B. herb (The "h" in "herb" is silent in American English, while in "send" and "sell" the initial consonants are pronounced.)

**Exercise 2: Choose the word whose main stressed syllable is placed differently from that of the others in each group.**

6. A. visit
B. follow
C. travel
D. enjoy

- Answer: D. enjoy (The stress is on the second syllable, while in "visit," "follow," and "travel" it is on the first syllable.)

7. A. family
B. tradition
C. family
D. festival

- Answer: B. tradition (The stress is on the second syllable, while in "family" and "festival" it is on the first syllable.)

8. A. library
B. vehicle
C. pollution
D. hospital

- Answer: C. pollution (The stress is on the second syllable, while in "library," "vehicle," and "hospital" it is on the first syllable.)

9. A. facility
B. activity
C. environment
D. transportation

- Answer: A. facility (The stress is on the second syllable, while in "activity," "environment," and "transportation" it is on the third syllable.)

10. A. hometown
B. weather
C. police
D. country

- Answer: C. police (The stress is on the second syllable, while in "hometown," "weather," and "country" it is on the first syllable.)