11.12

Surfing the Internet during class doesn't just steal focus from the educator; it also hurts students who are already struggling to grasp the material.在上课时上网不仅仅会转移老师的注意力，还会伤害到那些本来就对课堂内容理解有困难的学生。

Extinction is a difficult concept to grasp. It is an eternal concept.物种灭绝是个很难把握的概念。这个概念是永恒的。

Graphics are included not merely as a means of making the information easier for the student to grasp, but as an integral part of the way social scientists think.图表被包括在内不仅是作为一种使得信息对学生来说更容易掌握的手段，它还是社会科学家思考方式的主要部分。