B2 If you are doubtful about something, you are uncertain about it:
- It is doubtful whether the government will ever agree to their demands.
- We were doubtful about the product's usefulness from the start.
- It now looks doubtful that the building work will be completed on time.
- I'm a bit doubtful about whether to take on the job, as the hours are pretty unsociable.
- Many of us are doubtful about the value of these new educational strategies.
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