Located in the vast Atlantic Ocean, about seven miles off the coast of Venezuela,
is a small but fertile island that had retained from the period of its first discovery the name of Trinidad, and though picturesque, has rarely been visited by Europeans until the sixteenth century.
A. is a small but fertile island that had retained from the period of its first discovery the name of Trinidad, and though picturesque,
has rarely been-- has rarely been visited UNTIL the sixteenth century?
-- "has rarely been" refers to the recent and ongoing past, not 500 years ago.
Correct: The island has rarely been visited for the last 20 years. (recent past)
Correct: The island had rarely been visited by Europeans until 500 years ago, just a short while after they discovered it.
-- past perfect = past of the past and requires
one event rendered in simple past (discovered) OR
a time marker of some sort that points to a particular moment in time in the past
B.
was the small but fertile island of Trinidad, which retained its name from the period when it had first been discovered, and though picturesque, it had rarely been
-- nothing suggests that this island no longer exists
C. Trinidad is a small but fertile island that retains its name from the period of its first discovery, and though picturesque,
has rarely been-- same problem as that in A
D. is a small but fertile island, which has retained
from the period of its first discovery the name of Trinidad, and though picturesque, had rarely been
-- the best of a horrible lot of 5, but still flawed.
-- no reason exists to place the prepositional phrase between the verb and its object
E. the small but fertile island of Trinidad, retaining its name from the period of its first discovery,
though picturesque, rarely-- comma splice, visited modifies discovery (maybe), no verb in what should be a clause at the end (I think - what a mess)