Mettre le verbe au past perfect ou au present perfect

Sujet du devoir

a.The island......when the Bristish first settled in 1627.
( never be inhabited)

b. Christopher columbus.....America when the British settled in Barbados.
(already discover)

c.After slavery....., the sugar plantations needed lots of cheap labour.
(be abolished)

d. Since then, sugar and rum.....the main produces of the island.
(remain)

e. And social and political reforms......gradually. (be introduced)

f. Since 1966 the island......independent from the UK. (be)

g. In recent years production.......into light industry and tourism. (diversify)

Pouvez vous m'aider svp, je n'arrive pas a trouvé le bon temps pour chaque phrase :(

Où j'en suis dans mon devoir

Voila ce que j'ai mis mais je suis pas sure, et c'est incorrect:
a.has never been inhabited
b.had already discovery ou discovered
c.have been abolished ou was abolished
d.have remainded
e.have been introduced
f.have been
g.has diversified