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Hey everyone,

The OA is D. Here's my explanation adapted from the official one in the Beat The GMAT Practice Questions:

So let's see how we break down this argument. We know that the wolf population of a certain area can double every year, but they won't necessarily do that if the territory is too crowded. Lone wolves who can't get their own territory will move to places that are not so good, where they may be hunted by people.

A is not correct because it's not necessarily true, as stated in our first premise: while they can double every year (they'd quadruple in two years), this may not happen because of territory issues.

B can be eliminated because we're explicitly told in the argument that lone wolves are "unable to establish a territory near their place of origin". This does not mean that they're expelled from the pack just because the pack has doubled - maybe some wolves are chased away from the pack before the number doubles...

While we may feel like C is right because we know it's true from experience, there's nothing in the argument to suggest human encroachment on the wolves' territory.

D is actually the correct answer here. Even if some wolves are hunted down by humans, since the pack can double every year, the loss of a few wolves will be offset by the birth of new wolves. Take an example: suppose you start out with a pack of 15 wolves in a certain territory. 7 of them became aggressive and they had to be hunted down. We're left with 15 - 7 = 8 wolves in the pack. It's a great loss, but by the end of the year the pack can double. So the new number of wolves will be 2*8 = 16 wolves, which is pretty close to 15.

E kindda contradicts the passage. If the wolves double every year in a certain territory that's not yet full, then the density gets bigger and bigger.

Hope you liked this one!

Source: Beat The GMAT Practice Questions

Wolves can double their numbers every year. They do not do so, however, if the area in which they live is already full and the territory of each pack borders on the territory of other packs on all sides. Lone wolves, unable to establish a territory near their place of origin, disperse to a less desirable habitat and often are hunted by people.

Which of the following conclusions may be properly drawn from the information in the passage above?

A. The number of wolves in any area suitable for wolves may be predicted to quadruple in two years.
B. Wolves are ejected from the pack to wander singly as lone wolves when the number of wolves in the pack has doubled.
C. The amount of territory suitable for wolves has been diminishing in recent years as a result of human encroachment, with a resulting diminution in the wolf population.
D. Wolf hunting can continue at a moderate rate on the fringes of a good habitat for wolves without a decrease in the average yearly wolf population in that territory.
E. The wolf population density in a given area of wolf territory does not vary with the yearly rate of wolf reproduction.

It seems like everyone has already replied to this thread, but I thought I'd just drop my two cents anyhow .

(A) Not the answer

(A) doesn't work because the prompt simply says that wolves CAN double their numbers. It doesn't mean that they always do, even in suitable areas (from the prompt we learn more about unsuitable areas than suitable areas). Anyhow, once the wolves double their numbers after one year, how do we know the area is still suitable.

(D) THE ANSWER

While this one doesn't scream out as the answer, it doesn't overstretch either. Based on the fact that a good habitat is full, wolves hunted on the edge shouldn't effect the overall numbers. That is the density is slightly lowered, along a little wolf reproduction to make up for the hunted wolves. Again, not a resounding eureka, but the safest conclusion amongst the answer choices.

(E) Not the answer

From the short prompt we learn that density of wolves is correlated with reproduction. If an area is very dense, wolves do not reproduce as quickly. (E) says does not vary and is therefore incorrect.