Doubtful has 2 syllables and the stress is on the first syllable.
| # | Sentence | |
|---|---|---|
| 1. | One thing remains doubtful. | |
| 2. | I'm doubtful about what I ought to do. | |
| 3. | It is doubtful whether Bill will come. | |
| 4. | Mrs. Harris is very doubtful about her son's future. | |
| 5. | The correctness of the information is doubtful. | |
| 6. | It is doubtful whether the rumor is true or not. | |
| 7. | It is doubtful whether this will work. | |
| 8. | It is doubtful whether this method will work. | |
| 9. | It is doubtful whether this machine works well or not. | |
| 10. | It's doubtful if we'll finish in time for Christmas. |