Critical Reasoning (CR) | Re: A population of game ducks at a western lake contains

If time is tight—or you find that you cannot follow the argument as presented—this one is
practically screaming, “Skip me for now; come back to me later on.” Handling it requires a
firm grasp on the comparisons offered, as well as on the direct relationship that is the
author’s conclusion. Let’s start with that. According to the author, one will find a higher
percentage of older male ducks when there is a great disparity in sex ratios overall (i.e. all
males : all females). How come? Because among older ducks there are a lot more males,
whereas among younger ducks the male : female ratio is much closer to 1 : 1. In other
words, the more the male ducks strongly outnumber the females, the likelier it is that the
older males will outnumber the younger ones.

Compare the male : female ratio at the two lakes in question. The western lake’s is close to 1
: 1 (55 : 45), while the eastern lake’s is almost 2 : 1 (65 : 35). Which lake, according to the
conclusion, should have a greater percentage of older males? The eastern—that’s the lake
with the greater male : female disparity. So the western lake should have a lower percentage
of older males . . . and that’s just what (A) points out.
(B) The data in the argument compare the ages of adult and nonadult males. We cannot
draw (B)’s conclusion about adult vs. nonadult ducks—males and females combined.
(C) No conclusion about a total population can be drawn from a male : female ratio.
Contrary to (C), the western lake could have many more male ducks than the eastern, so
long as the western’s population reduces to 55 : 45 and the eastern’s to 65 : 35.
(D) introduces an issue—hatching time—that is totally removed from the argument. Hence,
(D) is completely unacceptable as an inference.
(E)’s conclusion about the age ratio of adult females : nonadult females is unjustified,
because no data comparing those groups are provided. The conclusion only concerns
males.