Here's the answer for each question based on the position of the primary stress:

**Question 1:**
- A. healthy (stress on the first syllable)
- B. culture (stress on the first syllable)
- C. habit (stress on the first syllable)
- D. unique (stress on the second syllable)

**Different word: D. unique**

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**Question 2:**
- A. pronounce (stress on the second syllable)
- B. promise (stress on the first syllable)
- C. attack (stress on the second syllable)
- D. maintain (stress on the second syllable)

**Different word: B. promise**

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**Question 3:**
- A. modern (stress on the first syllable)
- B. leisure (stress on the first syllable)
- C. behave (stress on the second syllable)
- D. certain (stress on the first syllable)

**Different word: C. behave**