请教prep上的一个语法题

bdx2010

66.   (答案是A我选了C，请NN指教，非常感谢)

 

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

bdx2010

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