Here are the answers for the question about the words with underlined parts pronounced differently:

1. **A. hour** - The underlined part "ou" is pronounced /aʊə/, while the others are pronounced /ʌ/ or /ɔː/.

2. **C. true** - The underlined part "ue" is pronounced /uː/, while the others have a different vowel sound.

3. **A. naked** - The underlined "a" is pronounced /eɪ/, while the others do not have the same vowel sound.

4. **A. brother** - The underlined "o" is pronounced /ʌ/, while others have different vowel sounds.

5. **A. led** - The underlined "e" is pronounced /ɛ/, while others have different vowel sounds.

6. **C. teacher** - The underlined "ea" is pronounced /iː/, while others have different sounds.

7. **C. cut** - The underlined "u" is pronounced /ʌ/, while others pronounce it differently.

8. **A. natural** - The underlined "a" is pronounced /æ/, while the others have different vowel sounds.

For the next section regarding filling in correct prepositions:

1. I’m surprised **at** the amount of money you have.
2. The children are really looking forward **to** their holiday.
3. Your dress is similar **to** mine but they are not exactly the same.
4. He's near-sighted. He hardly reads **his** glasses.
5. Tell me **just** one word what you want.
6. We can see many stars **over** our heads.
7. By mistake I opened Mary's letter instead **of** my own.
8. Shall we travel **in** your car or mine?

For the last part regarding the verb form:

1. Mary is grown up now. You shouldn’t speak to her as she **is** a child.