Поставьте частицу ‘to’ перед глаголом в скобках, где необходимо:
1. They were supposed (know) German well.
2. I didn’t expect her (marry) him.
3. She was seen (cross) the street and (turn) round the corner.
4. That is too heavy for one person (carry); let me (help) you.
5. He tried (make) me (believe) that he was my stepbrother.

С "let" никогда не берется частица "to".

1. They were supposed to knoe German well.2. I didn't expect her marry (marrying) him.3. -4. That is too heavy for one person to carry, let me help you.5. He tried to make me believe that he was my stepbrother.