Choose the correct preposition

1. Are you planning to return
   [to|back] Italy, Michael?
2. Fiona is in the living room chatting
   [by|with] her sister.
3. It's hard for little children to sit
   [up|through] a whole football match.
4. Julie has signed
   [with|up] for a creative writing course this year.
5. Remember to stop
   [off|down] at the grocer's on the way home ― we've run out of milk.
6. She was wearing a dress made
   [from|by] pure silk.