Sentence Correction

abhasjha wrote: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

What does option B mean?

Hi abhasjha,


Let's first understand the usage of the phrase 'that of':

"¢ The fixed costs of nuclear plants are more than that of other types of power plants. ('that' refers to 'the fixed costs')
"¢ The income of Raj is more than that of Mike. ('that' refers to 'the income' )

From these examples, we can see that "that of" is used to replace a noun that has already been used in the sentence. If we had not used "that" of in these sentences, they would have looked like this:

"¢ The fixed costs of nuclear plants are more than the fixed costs of other types of power plants.
"¢ The income of Raj is more than the income of Mike.


As you can see, we can use "that of" to replace nouns. Doing so prevents the sentence from sounding repetitive. However, note that we can only use "that of" when it is absolutely clear which noun it is referring to. We certainly cannot use it in a context in which it has no antecedent. For example, look at this incorrect sentence:

"¢ The number of apples in this crate is more than that of the number in that crate.

Now, what does "that of" refer to in this sentence? Absolutely nothing! The comparison is between "the number of apples in this crate" and "the number of apples in that crate". So, "that of" makes no sense here since there is nothing that it can refer to.

Now, in the given sentence:
"¢ Africa's black rhino population in the mid-1970s numbered about 20,000, ten times the estimated population of 2,000 in 1997.

The compared entities are:
1. Black rhino population in the mid-1970s i.e. 20,000
2. The estimated population in 1997 i.e. 2000


OPTION B
"¢ Africa's black rhino population in the mid-1970s numbered about 20,000, ten times that of their estimated population of 2,000 in 1997.

COMPARISON ERROR
There is no noun here that "that" can refer to. As you saw in the examples above, "that of" is used to replace a noun that has already been used in the sentence. Here, the comparison is between "the black rhino population" and "the estimated population". So, "that of" makes no sense since there is no logical antecedent that it can refer to.


PRONOUN ERROR
Also, there is no plural antecedent for the pronoun 'their'. It seems to refer to the black rhinos of Africa, but the noun "black rhinos" is not used in the sentence.



Hope this helps!
Regards,
Deepak