互动封闭仿真课堂
1、智能交互 2、电子板书式视频教学 3、在线互动问答 4、封闭课堂启发式教学方式
随堂测试、知识梳理、易错点揭示、总结启迪智能错题本
听课中的错题能自动加入错题本,课后可方便复习及导出错题本升级服务
在线答疑、课后同类题练习、讲义下载、短信提醒Pearl necklaces (珍珠项链) are very beautiful. Can you believe that these shining pearls 16 a kind of little animal named oyster? The animal lives in a shell (壳), deep down at the bottom 17 the sea. 18 do these beautiful pearls form (形成) inside an oyster? A grain (颗粒) of sand enters an oyster’s shell. This makes the oyster 19 . Just as 20 some dust
enters your eyes, your eyes will water and the tears (眼泪) from your eyes will try to 21 out the dust!
But when a grain of sand enters an oyster’s shell, it can’t wash it out. 22 , the oyster’s body keeps building a white 23 “coat” around the annoying sand. The coat covers the sand and 24 that makes a pearl.