雖然不敢說自己是有邏輯性思考的，但好歹自己頭腦也不算不清楚，但是GMAT的邏輯真的是要人命，得在一分鐘內解題，判讀句意選出正確答案，才有可能做完全部的題目，在這邊讓大家見識一下傳說中CR的威力，就不免理解我晚上上課會打瞌睡的原因。
The sustained massive use of pesticides in farming has two effects that are especially pernicious．First，it often kills off the pests’ natural enemies in the area．Second，it often unintentionally gives rise to insecticide resistant pests，since those insects that survive a particular insecticide will be the ones most resistant to it, and they are the ones left to breed．
From the passage above．it can be properly inferred that the effectiveness of the sustained massive use of pesticides can be extended by doing which of the following，assuming that each is a realistic possibility?
(A) Using only chemically stable insecticides
(B) Periodically switching the type of insecticide used
(C) Gradually increasing the quantities of pesticides used
(D) Leaving a few fields fallow every year
(E) Breeding higher-yielding varieties of crop plants
