The doctors did all they could, but he finally cancer.
The correct answer will be option A because here in the question they have indicated about the death of the person. The other options (asked for, fell back into & came into) are not fitting for this question. So, the correct answer is <u>A.</u><u> </u><u>died </u><u>of </u>(✓).
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Hope it helps.
RainbowSalt2222