It is a tough problem for teaching staff that there is the shortage of emotional communication caused by the separation of teachers and learners in E-learning environment.

在网络学习环境中，由于师生时空分离而导致的情感交流缺失一直是困扰广大远程教育工作者的一个难题。

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It is a tough problem for teaching staff that there is the shortage of emotional communication caused by the separation of teachers and learners in online Learning environment.

在网络学习环境中，师生时空分离而导致的情感交流缺失一直是困扰广大远程教育工作者的一个难题。

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The measure of success is not whether you have a tough problem to deal with, but whether it is the same problem you had last year.

衡量成功，不是看你是否要处理棘手的问题，而是你是否要处理和去年同样的问题。

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For regulators, it is a tough problem.

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The real problem for Apple is that it's tough to build a smart phone that can compete with the ease of use of a simple flip phone equipped with buttons.

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