Although he is as gifted as, if not more gifted than, many of his colleagues, he is extremely modest and his poetry is unpublished(A) Although he is as gifted as, if not more gifted than, many of his colleagues, he is extremely modest and his poetry is unpublished.
(B) Although he is as gifted, if not more gifted, than many of his colleagues, he is extremely modest and with his poetry remaining unpublished.
(C) Although he is as gifted as, if not more gifted than, many of his colleagues, he is extremely modest and will not publish his poetry.
(D) Despite his being gifted, if not more gifted than his colleagues, he is extremely modest and will not publish his poetry.
(E) Being a gifted as, or more gifted than, many of his colleagues, he is extremely modest and his poetry is unpublished.
Let us take this short route to solve this question. Look at the construction:
Although he is X, he is also Y, and (therefore) he will not do Z. The part after the conjunction 'and' should be one that he himself does. Therefore, we can safely remove, e A, B and E. Between C and D, we can simply kick out D for using 'being' as a modifier. C remains.
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