新东方材料279页第152题（全文划线）

152. Certain pesticides can become ineffective if used repeatedly in the same place: one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.

A) Certain pesticides can become ineffective if used repeatedly in the same place: one reason is suggested by the finding that there are much larger populations of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.

B) If used repeatedly in the same place, one reason that certain pesticides can become ineffective is suggested by the finding that much larger population of pesticide-degrading microbes in soils with a relatively long history of pesticide use than in soils that are free of such chemicals.

答案是A，但是不太理解B为什么错了，是改变语意了吗？

提前谢过~~~~