This is my pen, it is blue, my mother bought it yesterday. It is very useful, I like it very much.

这是我的钢笔,它是蓝色的,我的妈妈昨天买的. 它是很有用的,我非常喜欢它.

This is a Chinese book, it is my book, it is a new book , it is a very interesting book, I like it very much

这是一本语文书,它是我的书,它是一本新书,它是很有趣的一本书,我非常喜欢它

Suppose someone gave you a pen - a sealed, solid-colored pen.

假如有人送你一支笔，一支不可拆卸的单色钢笔。