对任意两个非零的平面向量$\overrightarrow{\alpha }$和$\overrightarrow{\beta }$，定义$\overrightarrow{\alpha }\circ \overrightarrow{\beta }=\frac{\overrightarrow{\alpha }·\overrightarrow{\beta }}{\overrightarrow{\beta }·\overrightarrow{\beta }}$．若平面向量$\overrightarrow{a},\overrightarrow{b}$满足$\left|\overrightarrow{a}\right|\ge \left|\overrightarrow{b}\right|>0$，$\overrightarrow{a}$与$\overrightarrow{b}$的夹角$\theta \in \left(0,\frac{\pi }{4}\right)$，且$\overrightarrow{a}\circ \overrightarrow{b}$和$\overrightarrow{b}\circ \overrightarrow{a}$都在集合$\left\{\frac{n}{2}|n\in Z\right\}$中，则$\overrightarrow{a}\circ \overrightarrow{b}$=

新疆的哈密瓜因甜度大而著称，有人将其引进到本地种植，其果实甜度大大降低，再引种回新疆种植，果实又恢复到以往的甜度，从哈密瓜引种的过程看出（　　）

根据短文内容，完成下列小题。

        Most middle school students wear uniforms. Some students like uniforms, but others don't. However, recently, a Japanese government survey (政府调查) shows that more students in Japan like uniforms now because school uniforms are more fashionable(时尚的) than they were before.

        I surveyed some Japanese students about what they thought about school uniforms. I asked them, “Are fashionable uniforms popular or not?” There were lots of different opinions(观点,看法).

        Hiromi said, “I like school uniforms because I don't need to choose clothes every day. I think that fashionable uniforms are good. My high school uniform is fashionable, but there is a problem. Fashionable uniforms are too expensive.”

        Miki said that she didn't like fashionable uniforms because she didn't want to spend so much money on uniforms. She thought that the uniforms should be changed(被改变). They should be cheaper and easier to get.

        Mitsuaki said, “I don't like school uniforms because I want to look different. I also agree that fashionable uniforms make many students want to wear uniforms in high school. If students like fashionable uniforms, it is good.”