单项选择题
A.cause no damageB.cause the most damageC.cause less agricultural damage than the many smaller,more frequent floodsD.far exceed the smaller,more frequent floods in agricultural loss
A.they replenish the soilB.they do not prevent the loss of soilC.they are destroying the ecologyD.they pollute the nation’s water supply
A.planting less corn and soybeanB.putting fertilizers on their fieldsC.preventing soil erosionD.decreasing the supply of top soil