Here are the words that differ from the others in terms of primary stress:

1. **C**. balance (primary stress on the first syllable, while the others have stress on the second syllable)
2. **D**. exist (primary stress on the second syllable, while the others have stress on the first syllable)
3. **B**. solution (primary stress on the second syllable, while the others have stress on the first syllable)
4. **A**. access (primary stress on the first syllable, while the others have stress on the second syllable)
5. **A**. convenient (primary stress on the second syllable, while the others have stress on the first syllable)
6. **B**. connect (primary stress on the second syllable, while the others have stress on the first syllable)
7. **C**. concentrate (primary stress on the first syllable, while the others have stress on the second syllable)
8. **C**. avoid (primary stress on the second syllable, while the others have stress on the first syllable)
9. **C**. explore (primary stress on the second syllable, while the others have stress on the first syllable)
10. **D**. pressure (primary stress on the first syllable, while the others have stress on the second syllable)

These selections are based on the placement of the primary stress in each word.