经济受害允许水平
参考答案：
作物因虫害造成的损失与防治费用相等的那个关键性种群密度或作物受损害的程度。
Neither I nor he ______ compared the prices of the PC, so ______ he ______ I decided to know more before buying it.
A．has; both; and
B．have; not only; but also
C．hasn’t; either; or
D．haven’t; neither; nor
青霉素降解产物可引起
A．哮喘B．甲亢患者C．荨麻疹D．过敏性休克E．假膜性肠炎
