Africa’s black rhino population in the mid

[manhhiep2509]

Africa's black rhino population in the mid-1970's numbered about 2,000, 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

Hi.

in choice D, I think that "more black rhinos than" is incorrect because the sentence is comparing real numbers of the animal and the estimated numbers. But, the choice seems to compare the animal and the estimated numbers.

Is my understanding correct?

[Bill@VeritasPrep]

I think the biggest problem with D is "their". It makes it sound like the rhinos made the population estimate themselves