程颢、程颐兄弟认为，不是物喜己悲之乐，而是悟本达源之乐、超凡脱俗之乐，这种至善圆满之乐是建立在觉悟“自心”基础上的。这反映出（    ）

小华同学学习了细菌和真菌的知识后，设计了以下实验，探究酵母菌的发酵过程是否需要适宜的温度．具体实验设置如图，3个小时后，发现甲烧瓶上原来被挤瘪了的气球鼓了起来，乙烧瓶上的气球并没有鼓起来．分析实验，回答问题．

科技书9.80元/本，故事书8.50元/本，两本书共____元，两本书相差____元。

已知D是△ABC中边BC上的中点，若 $\overrightarrow{AB}$ = $\overrightarrow{a}$ ， $\overrightarrow{AC}$ = $\overrightarrow{b}$ ，则 $\overrightarrow{AD}$ =（   ）

阅读理解
   The best thing about going to school is learning how to read. Books are great friends. They can help you to learn about anything you want to know. They can go anywhere with you. You can read about animals, faraway places, people, and anything else.
   Books are written by people called authors(作者). Authors think of things they want to write about. They make a plan for a book and start to write .Some authors write books that give us information(信息)and teach us things. Authors are very important people because they help us learn. Find a good book to read and read every day ,You will enjoy your time with a good book.