Bonjour!
1- ∅ (il y' a déjà la contraction <<'s>> de "is")
2- He's been working in the garden and
3- he hasn't eaten anything yet.
4- ∅
5- his mother and his sister are preparing the meal together and
6- they haven't finished yet.
7- It will probably be ready at half past eight
8- ∅
J'espère que ça t'aidera :)
