读《伊索寓言》一则，在横线上归纳出寓意。
寓意是：
寓意是：事物总在不断变化，不可能一劳永逸。
Almost every developing country went through a period ______ pollution became serious with the
rapid development.[ ]
A. where
B. whose
C. of which
D. in which
材料员要服从( )的安排，根据工程进度计划和材料采购单采购到既合格又经济的材料。
A．项目经理B．建造师C．公司经理D．工地负责人
