1.go back to 回去；归

I'll go back to the appfog example.
现在回到最开始的那个appfog的故事。

Go back to your tents!
回你的帐篷去！

2.free to 免费

Feel free to share in the comments area.
请在下面的评论区域自由分享。

A gyroscope is just a spinning wheel that is free to rotate.
陀螺就是一个可以自由旋转的转动着的轮子。

3.primary school 小学，初等学校

Nobody in her family has ever finished primary school.
她的家庭中没有人完成过小学学业。

The design and strategy of primary school outside reading network.
小学生课外阅读网络化的教学设计及策略。

4.senior school 大龄儿童学校；高中

Improving senior school students reading ability by extensive reading.
通过泛读提高高中学生的阅读能力。

For example, lower grade pupils study for praise of teachers and parents. While, higher grade pupils study to get outstanding scores to enter a key senior school instead of hoping to get praise.
比如低年级的小学生，其主导性学习动机可能仅仅是为了得到教师和家长的夸奖，而小学高年级学生学习的主导性动机即不再是为了得到夸奖，而是为了获得优异成绩，以便进入重点中学。