The Scandinavian assault on western Europe culminated in the early eleventh century with the Danish conquest of the English Kingdom,which other Scandinavian kings attempted to repeat,unsuccessfully,later in the same century.

(A)which other Scandinavian kings attempted to repeat,unsuccessfully,later in the same century.
(B)which other Scandinavian kings attempted to repeat later that same century,but not successfully
(C)an achievement that other Scandinavian kings attempted later in the century to repeat,but were not successful at it
(D)an achievement attempted later in the century by other Scandinavian kings that was not successful
(E)an achievement that other Scandinavian kings attempted to repeat later in the century,but without success.

In option e, shouldn't we have a independent clause after but? Also, why is d wrong?