Choose the word or set of words that, when inserted in the sentence, best fits the meaning of the sentence as a whole.

Bolstered by his unflagging determination and ------- physical preparation, Tom Whittaker became the first amputee to successfully climb to the summit of Mount Everest.

(A) fortuitous
(B) assiduous
(C) heedless
(D) expeditious
(E) pedantic

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