Read the sentences and choose the correct variant.
1. I am ____ loss, I don't know what to do.
2. It didn't happen yesterday but the day ____ yesterday.
3. We will know everything ____ he comes.
4. You must check the petrol ____ regular intervals.
5. I lost my passport _____ the way to Madrid.
6. Some people are _____ prison for crimes they have not committed.