Answer Choice A

I was similarly confused as Emily. The wording in the passage talks about "older" and "adult" vs "young" and "not yet bred." Are we supposed to assume that young and not yet bred are categorized the same? A duck may not have bred yet, but that doesn't necessarily mean that it is young. This also made me think that A was wrong due to the wording.

Any ideas?

@EmilyMarieMenendez, this is a tricky one because it throws a lot of quantifiers at you. However, there are a few pieces of information that help clear it up. First, with the discussion of young, old, adult, not-yet-bred, etc. there are a few things that help clear it up. To start, the second sentence directly contrasts the ratio of ducks "that have not yet bred" with "older ducks." This, combined with the following sentence that interprets the same data in terms of "adult ducks" and "young ducks," suggests that "young ducks" are those "that have not yet bred," and "adult ducks" are "older ducks." There may be a few adult ducks that have not yet bred, but from the discussion, it doesn't seem to be many. Given that we're talking about "young ducks" that have only slightly more males than females and "adult ducks" that are have significantly more males than females, (A) is the correct answer because it can be 100% inferred from the above information. If young ducks are pretty close to a 50-50 split on male and female, then the higher the percentage of male ducks in a lake, the higher the percentage of older ducks there must be. (C) is wrong because it moves from percentages to actual numbers, and you cannot back that up with information from the passage. It is possible that there are 1,000 ducks at the Western lake, meaning there are 550 male ducks, while there are only 100 ducks at the Eastern lake, meaning there are only 65 male ducks there. The percentage of males is higher, but that doesn't guarantee that the total number is higher. Hope that helps.