设向量 $\overrightarrow{e_1}$ ， $\overrightarrow{e_2}$ 是夹角为 $\frac{2\pi }{3}$ 的单位向量，若 $\overrightarrow{a}$ = $\overrightarrow{e_1}$ + $\overrightarrow{e_2}$ ，则| $\overrightarrow{a}$ |=____．

党的十八大报告中指出：“教育是民族振兴和社会进步的基石。……要大力促进教育公平，合理配置教育资源……”孔子的下列观点中，最能体现报告精神的是（    ）

如图是某同学的学习笔记，根据所示内容判断与他笔记相关的历史人物是（    ）

根据短文内容，从A、B、C、D四个选项中选择一个最佳答案。
Passage 1
     Steven Jobs, the designer of Apple Computer, was not clever when he was in school. At that time, he was not a good student and he always made troubles with his schoolmates. When he went into college, he didn't change a lot. Then he dropped out（退学）. But he was full of new ideas.
　 After he left college, Steven Jobs worked as a video game designer. He worked there for only several months and then he went to India. He hoped that the trip would give him some new ideas and give him a change in his life.
　 Steven Jobs lived on a farm in California for a year after he returned from India.
　 In 1975, he began to make a new type of computer. He designed the Apple Computer with his friend in his garage. He chose the name “Apple” just because it could help him to remember a happy summer he once spent in an apple tree garden.
His Apple Computer was so successful that Steven Jobs soon became famous all over the world .
He often said, “I live in order to change the world, there aren't any other reasons. The only way to have a great achievement is to love your own career. If you can't find your  favorite career ,go on looking for it and never give up.”
     This is Steven Jobs, though he is dead, his spirit and achievements still influence our lives.

下列做法利用物态变化放热的是（     ）