According to this excerpt, which of these best identifies the effect of the growing swarms of bees?

Here is the excerpt he/she was talking about

Excerpt from A Tour of the Prairies

Washington Irving

It is surprising in what countless swarms the bees have overspread the far west, within but a moderate number of years. The Indians consider them the harbinger of the white man, as the Buffalo is of the red man; and say that, in proportion as the bee advances, the Indian and Buffalo retire.

And here's the question

According to this excerpt, which of these BEST identifies the effect of the growing swarms of bees?

A) The number of bees and buffaloes is reduced.

B) The number of buffaloes and Indians is reduced.

C) The number of bees and buffaloes is increased.

D) The number of bees increase with the number of buffalo.

And the correct answer would be

B) The number of buffaloes and Indians is reduced.