Réponse :
1) I thought I HAD SEEN
2) convicts HAD BEEN TRANSPORTED
3) children HAD LIVED // Government HAD DECIDED
4) He HADN'T ENJOYED
Explications :
La structure d'une phrase au past perfect :
Première position; le sujet.
Deuxième position; le verbe have -> had
Troisième position; participe passé.