Fill the gaps with the modals can and must or their equivalents. In some sentences more than one variant is possible.
1    I go to the swimming pool three times a week. 1 hope I ... swim quite well by next summer.
2    Do you know that cats ... see very well in the dark?
3    Some animals ... do without food for a very long time. Snakes, for example____survive the whole winter without eating.
4    When I was a little girl, I ... do acrobatic feats (трюки), but now I can't.
5    There are no tickets for our flight so we ... go by train.
6    If there is not going to be any information about those passengers till tomorrow morning, we ... call the police.