Bonjour !
a. Rory's farm is the most isolated farm I have ever seen.
b. Living with cows has been the greatest experience she has ever had.
c. Mustering the cattle has been the most exciting thing they have ever did.
d. The School of the Air is the funniest school he has ever been to.
Explications :
Adjectifs courts : the + adjectif + est (great => the greatest)
Adjectifs courts se terminant par -y : the + adjectif + i + est (funny => the funniest)
Adjectifs longs : the + most + adjectif (isolated => the most isolated)
J'espère t'avoir aidé. Bon courage !