**Here are some examples of using the word «doubtful» in English:**
1. I'm **doubtful** whether she will be able to finish the project on time.
2. It is **doubtful** that we will have enough money to go on vacation this year.
3. He looked at me with a **doubtful** expression on his face.
4. The chances of winning the lottery are very **doubtful**.
5. She was **doubtful** about her decision to quit her job and start her own business.
6. The weather forecast is **doubtful**, so we should be prepared for anything.
7. He gave a **doubtful** shrug and walked away.
8. The company's financial situation is **doubtful**, and there are rumors of bankruptcy.
9. She had **doubtful** feelings about the new employee, but she didn't want to be rude.
10. It is **doubtful** that they will be able to find a suitable replacement in such a short time.