Africa's black rhino population in the mid-1970's numbered about 20,000, ten times the estimated population of 2,000 in 1997.
the estimated population
that of their estimated population
more than the population's estimated amount
more black rhinos than their population estimate
more than that of their population's estimated amount
如果用more than结构的话,应该是 nine times more than that of 2000 in 1997.不知道对不对?
可以。
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