AXAN
Is "Black Rhino" in this question singular or plural? How do we decide which is it?
Why is D incorrect?
Can "more" be seen as an eliminating factor, since "ten times more" would actually mean eleven times when we actually want to say ten.
In B, is "that" functioning as a pronoun and can we eliminate B on the basis that there is no clear antecedent it could be referring to?
Good questions,
AXAN. Notice, first, that
black rhino is used as an adjective to define a particular
population, and in such a context, we use the singular noun form for that adjective. For instance, we say
the human population, not
the humans population. Thus, the sentence should not use
their to refer to the black rhino as a species. Answer choice (D) would already be out of the running. Still, and to touch on some of your other questions, we cannot ignore
more at the head of answer choices (C) through (E). Since
ten times can function as a comparative without
more,
ten times more introduces a redundancy that is better avoided. Besides, the GMAT™ tightly governs elements in a comparison, and since the first element is
population, so, too, should be the second. Follow the nouns to tell what is being compared. Answer choice (C) refers to an
amount; (D) to
black rhinos and an
estimate in some sort of lopsided comparison; and (E) to
that and, again, an
amount. Finally, in answer choice (B),
that should have a logical antecedent that we can substitute in, and here, we would be looking for a singular noun. The only such word I can find earlier in the sentence is
population, and it makes no sense to say
[the population] of their estimated population. You cannot substitute
the number as a derivative of the earlier
numbered just to patch things up.
That is more restricted in use on this test. In short:
Quote:
Africa's black rhino population in the mid-1970's numbered about 20,000, ten times the estimated population of 2,000 in 1997.
(A) the estimated population
(B) that of their estimated population
(C) more than the population's estimated amount
(D) more black rhinos than their population estimate
(E) more than that of their population's estimated amount
Perhaps the question makes more sense now. Comparisons are heavily tested, so they are worth careful study.
- Andrew