1. He doesn't know the answer to this question. Does he know the answer to this question?
2. He doesn't leave home at eight o'clock. Does he leave home at eight o'clock?
3. The last train doesn't arrive at midnight. Does the last train arrive at midnight?
4. It is not important to choose a good job. Is it important to choose a good job?
5. They don't refuse to help us. Do they refuse to help us?
6. This job doesn't suit his abilities well enough. Does this job suit his abilities well enough?