II. Pick out the word whose stress is placed differently from the others in each group.
1. A. expectation ; B. introduction ; C. volunteer ; D. foundation
2. A. extensive ; B. exciting ; C.excellent ; D. existent
3. A. sucessful ; B. wonderful ; C. beautiful ; D. plentiful
4. A. mechanic ; B. offical ; C. preference ; D. convenience
5. A. attract ; B. service ; C. appeal ; D. revolve