Sure, I'll help you identify the word that differs in the position of the primary stress in each of the following questions:

1. A. control (stress on the second syllable)
B. exchange (stress on the second syllable)
C. focus (stress on the first syllable) - **Answer**
D. install (stress on the second syllable)

2. A. upload (stress on the second syllable)
B. prepare (stress on the second syllable)
C. discuss (stress on the second syllable)
D. textbook (stress on the first syllable) - **Answer**

3. A. digital (stress on the first syllable) - **Answer**
B. schedule (stress on the first syllable)
C. strategy (stress on the first syllable)
D. distraction (stress on the second syllable)

4. A. digital (stress on the first syllable)
B. personal (stress on the first syllable)
C. excellent (stress on the first syllable)
D. effective (stress on the second syllable) - **Answer**

5. A. similar (stress on the first syllable)
B. national (stress on the first syllable)
C. effective (stress on the second syllable) - **Answer**
D. interesting (stress on the first syllable)

6. A. exercise (stress on the first syllable)
B. volunteer (stress on the third syllable) - **Answer**
C. national (stress on the first syllable)
D. interview (stress on the first syllable)

7. A. balance (stress on the first syllable)
B. issue (stress on the first syllable)
C. panda (stress on the first syllable)
D. extreme (stress on the second syllable) - **Answer**

8. A. serious (stress on the first syllable)
B. influence (stress on the first syllable)
C. energy (stress on the first syllable)
D. pollutant (stress on the second syllable) - **Answer**

9. A. promote (stress on the second syllable) - **Answer**
B. support (stress on the second syllable)
C. research (stress on the second syllable)
D. nature (stress on the first syllable)

10. A. aware (stress on the second syllable) - **Answer**
B. protect (stress on the second syllable)
C. impact (stress on the first syllable)
D. danger (stress on the first syllable)

11. A. solution (stress on the second syllable) - **Answer**
B. habitat (stress on the first syllable)
C. endangered (stress on the second syllable)
D. awareness (stress on the second syllable)

12. A. natural (stress on the first syllable)
B. chemical (stress on the first syllable)
C. atmosphere (stress on the first syllable)
D. solution (stress on the second syllable) - **Answer**

13. A. profit (stress on the first syllable)
B. protect (stress on the second syllable) - **Answer**
C. local (stress on the first syllable)
D. impact (stress on the first syllable)

14. A. ecotourism (stress on the second syllable)
B. relaxation (stress on the third syllable) - **Answer**
C. preservation (stress on the third syllable)
D. disappointed (stress on the third syllable)

15. A. tradition (stress on the second syllable) - **Answer**
B. stalactite (stress on the second syllable)
C. cultural (stress on the first syllable)
D. industry (stress on the first syllable)

I hope this helps!