Official Explanation
Answer: (E)
The argument is that the elk’s territory will grow because the elderberry, its primary food source, is expected to grow further north. (E) calls this conclusion into question because if elderberries can no longer grow in the southern half of the elk’s territory, then the elk's range has been truncated. There is no information concerning how far north the new territory will reach.
(A) suggests that elk will be very well provided for, diet-wise, as they move into the tundra.
(B) is just a general fact that does not relate to the argument.
(C) may be tempting but remember that just because the grizzly bear will continue to prey on the elk as it moves into the tundra does not mean there will be no elk in the tundra.
(D) is out of scope because the argument only concerns the tundra, not the area north of the tundra.
FAQ: Can you explain choice A a bit more?A: (A) reads: In addition to elderberry, the Canadian elk also consumes loganberries, which are expected to also begin growing at more northerly latitudes.
The key here is that another of the elk's food sources is going to grow in the north. This simply strengthens the argument that the elk's range will increase (into the north).
In order to weaken the argument, we need to look for a reason that the elk's range would actually not increase. (A) does not provide such a reason -- it provides another reason why the elk's range will increase.
FAQ: Can you explain choice C a bit more?A: (C) may be tempting, but remember that just because the grizzly bear will continue to prey on the elk as it moves into the tundra does not mean there will be no elk in the tundra. The grizzly bears will not stop the elk from moving north. Rather, the grizzly bear would follow the elk north. The elk's range would still expand into new regions.
FAQ: What about D?A: This isn't negating the facts of the passage. The passage says the elderberries have spread into the TUNDRA, but (D) is talking about ABOVE the tundra...in other words, even farther north of the tundra.
So the elderberries are still spreading. (D) doesn't contradict this, it just puts one kind of limit on how far/how much the elderberries and therefore the elk could spread. But this doesn't weaken the argument that the elk's territory will increase at least to some degree. They are still spreading to part of the tundra.