[求助]sec3-5句子改错求助

South Korea has witnessed the world’s most dramatic growth of Christian
congregations; church membership is expanding by 6.6 percent a year, fully
two-thirds of the growth coming from conversions rather than the population
increasing.

(A) coming from
conversions rather than the population increasing

(B) coming from
conversions rather than increases in the population

(C) coming from
conversions instead of the population’s increasing

(D) is from
conversions instead of population increases（B）

(E) is from
conversions rather than increasing the population

答案是B,讨论贴里没有找到。我的疑问是A和B中，为什么用increases in the population 而不用 the population increasing.

请高手指点，谢谢