(1) The causal relationship could be reversed—maybe having a higher-paying job allows people to own laptops, not the other way around.
(2) Some other, underlying factor could be causing the correlation—maybe there’s something that causes people to both have higher-paying jobs and own laptops.
A
It attempts to support a sweeping generalization on the basis of information about only a small number of individuals.
B
Its conclusion merely restates a claim made earlier in the argument.
C
It concludes that one thing was caused by another although the evidence given is consistent with the first thing’s having caused the second.
D
It offers information as support for a conclusion when that information actually shows that the conclusion is false.
E
It uncritically projects currently existing trends indefinitely into the future.
Mature white pines intercept almost all the sunlight that shines on them. They leave a deep litter that dries readily, and they grow to prodigious height so that, even when there are large gaps in a stand of such trees, little light reaches the forest floor. For this reason white pines cannot regenerate in their own shade. Thus, when in a dense forest a stand of trees consists of nothing but mature white pines, it is a fair bet that _______.
Summary
Mature white pines intercept almost all the sunlight they receive. They leave a deep litter and grow tall enough so that little light reaches the forest floor even with little gaps between trees. White pines cannot regenerate in their own shade.
Strongly Supported Conclusions
In a forest of mature white pines, it is unlikely that any adjacent pines differ widely in age.
A
the ages of the trees in the stand do not differ from each other by much more than the length of time it takes a white pine to grow to maturity
This is strongly supported because we know that mature white pines next to each other leave so little sunlight on the forest floor that white pines cannot regenerate. This would prevent young trees from emerging where pines are already mature.
B
the land on which the stand is now growing had been cleared of all trees at the time when the first of the white pines started growing
This is unsupported because it is not required that all white pines are cleared for new ones to grow. The stimulus only tells us that stands of mature white pines prevent regeneration.
C
competition among the trees in the stand for sunlight will soon result in some trees’ dying and the stand thus becoming thinner
This is unsupported because even though the competition for sunlight may prevent new white pines from growing between mature trees, we have no reason to suspect that already mature trees will compete with each other for sunlight.
D
other species of trees will soon begin to colonize the stand, eventually replacing all of the white pines
This is unsupported because the stimulus provides no information on other trees outcompeting stands of mature white pines.
E
any differences in the heights of the trees in the stand are attributable solely to differences in the ages of the trees
This is unsupported because we don’t know that there aren’t other factors like rain or nutrition that contribute to height differences.