A:信息传递
B:能量流动
C:物质循环
D:食物链和食物网
把1千克、0.56千克、0.6千克、1千克20克从大到小排列是:____>____>____>____。
海陆变迁的主要原因有①气候变化 ② 人类活动 ③ 地壳的变动 ④ 海平面的升降
完型填空
1 is an American girl. 2 name is Helen. And this is Mike. 3 is an English boy. Mike can 4 his name. Kate can sing ABC song. Mike's home phone number is 658-4323. He can5Kate at 954-3643. They6friends now.