Mark the letter A,B,C or D to indicate the word that differs from the other three in the position of the main stress in each of the following questions
1. D. offer
2. C. preferential
3. C. inventor
4. B. unemployment
5. D. mosquito
6. B. intensity
7. C. researcher
8. B. optimistic
9. B. happen
10. A. represent
11. A. minister
12. A. equip
13. D. comment
14. B. inflation
15. C. cement
16. B. achievement
17. D. subtract
18. B. activity
