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② call on / upon sb. to do sth. 请/叫某人做某事He called upon me to speak immediately.
③ 号召;呼吁;要求 The President called on his people to serve the country.
(3) call up
① 给……打电话 (英 ring up) I tried to call you up last night, but no one answered the phone.
② 征召入役;调用 (后备部队) Three boys in our street were called up last week.
4. be afraid, be afraid to do sth., be afraid of (doing) sth.
(1) be afraid 意为“担心，害怕”，多用于口语，常用来表示一种歉意，或遗憾，后可接 so 或 not，也可接 that 从句。I'm afraid (that) 其语意相当于 I'm sorry, but...。
-- Are we on time? 我们准时吗? -- I'm afraid not. 恐怕不准时。I'm afraid you'll get caught in the rain.
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