Move back and forth like a ship.

像船一样来回地移动。

82. balance between ...之间的平衡

At times like that you have to strike a balance between sleep and homework.

在这种情况下，你得在休息和做作业之间找到一种平衡。

83. barrier to ...的障碍

The greatest barrier to success is the fear of failure.

成功最大的障碍就是对失败的恐惧。

84. be based on 以...为基础

Scientific theories must be based on facts.

科学理论必须以事实为根据。

85. bear／keep in mind记住

You must bear in mind that your parents expect you to become a good doctor.

你要记住你的父母希望你成为一名好医生。