A:What did you have for breakfast?
B:Where did you go this morning?
C:What did you have for supper?
如图是某温带草原生态系统中的食物网简图,请据图分析回答:
生活中常常会发生一些变化,下列变化属于化学变化的是( )
我国著名科学家王选因发明汉字激光排照技术大大提高了印刷效率而被誉为“当代毕升”。印刷术是我国四大发明之一,目前世界上现存最早,标有确切日期的雕版印刷品是( )