I can / I can't

1 . I can't come now , but I ____________________ come tomorrow .
2 . I haven't got a computer , so I ____________________ surf the web .
3 . She's a really good runner - she ____________________ run a marathon in around 3 hours .
4 . My cat can't swim but it ____________________ climb trees .
5 . My little sister's three years old . She can walk but she ____________________ read .