Answer:
(A) Any sickness, as the word 'other' should be in between, it makes more sense.
Explanation:
<span>Victor - a person who defeats an enemy or opponent in a battle, game, or other competition.
</span><span>Enter - begin to be involved in.
</span>In this case (because of the 2 words), I think that the victor is the person who wins the competition while the word enter, or the phrase to enter, is probably meant as in to enter the competition. The question wasn't entirely clear but I hope I have sort of answered it. :)
He is planning the windmill
1st: drawing inferences
2nd: testing a hypothesis
3rd: recognizing a problem
