Ex 3 : 1. HAD parce que c'est she had discovered = le participe passé*
2. WOULD
Ex 4 : c. he hadn't the opportunity to go.
d. she hadn't expected him to answer.
Ex 5 : a. realized - had left
b. arrived - hadn't/had not
c. didn't know - did - burst
(je ne suis sûre de rien)