Let's analyze the pronunciation of the underlined parts in the words given:

1. **Choose the word whose underlined part is pronounced differently from that of the others:**

- A. beehive
- B. envious
- C. kite
- D. horizon

The underlined parts are:
- A. beehive: "bee"
- B. envious: "en"
- C. kite: "kite"
- D. horizon: "ho"

The word "envious" has a different vowel sound compared to the others. The correct answer is **B. envious**.

2. **Choose the word whose underlined part is pronounced differently from that of the others:**

- A. celebrity
- B. picturesque
- C. hospitable
- D. cultivate

The underlined parts are:
- A. celebrity: "ce"
- B. picturesque: "pic"
- C. hospitable: "hos"
- D. cultivate: "cul"

The word "picturesque" has a different vowel sound compared to the others. The correct answer is **B. picturesque**.

3. **Choose the word whose underlined part is pronounced differently from that of the others:**

- A. technical
- B. competitor
- C. timber
- D. facility

The underlined parts are:
- A. technical: "tech"
- B. competitor: "com"
- C. timber: "tim"
- D. facility: "fa"

The word "facility" has a different vowel sound compared to the others. The correct answer is **D. facility**.

4. **Choose the word which is stressed differently from the others:**

- A. dweller
- B. area
- C. transport
- D. lighthouse

The stress patterns are:
- A. dweller: stress on the first syllable
- B. area: stress on the first syllable
- C. transport: stress on the first syllable
- D. lighthouse: stress on the first syllable

All words have the stress on the first syllable. There is no word with a different stress pattern in this set.

5. **Choose the word which is stressed differently from the others:**

- A. urbanization
- B. countryside
- C. grassland
- D. household

The stress patterns are:
- A. urbanization: stress on the fourth syllable
- B. countryside: stress on the first syllable
- C. grassland: stress on the first syllable
- D. household: stress on the first syllable

The word "urbanization" has a different stress pattern compared to the others. The correct answer is **A. urbanization**.

6. **Choose the word which is stressed differently from the others:**

- A. associate
- B. combine
- C. picturesque
- D. experience

The stress patterns are:
- A. associate: stress on the second syllable
- B. combine: stress on the second syllable
- C. picturesque: stress on the third syllable
- D. experience: stress on the second syllable

The word "picturesque" has a different stress pattern compared to the others. The correct answer is **C. picturesque**.