$\overrightarrow{a}$，$\overrightarrow{b}$为平面向量，已知$\overrightarrow{a}=\left(4,3\right),2\overrightarrow{a}+\overrightarrow{b}=\left(3,18\right)$，则$\overrightarrow{a}$，$\overrightarrow{b}$夹角的余弦值等于（   ）.

物体A和B相对静止，以共同的速度沿斜面匀速下滑，则（   ）

如图为人体内淋巴细胞生成过程及某特异性免疫反应示意图，请据图回答下列问题：

（1）免疫系统由免疫器官、免疫细胞和____ 组成，图中所示的免疫器官有____ （填名称）．

（2）细胞D的增殖、分化需要____ 的刺激或作用，细胞E在图中所示的免疫过程中所起的作用为____ 

（3）刺参含酸性粘多糖和海参皂苷等多种生物活性物质．某研究小组以小鼠为实验材料，对刺参的抗肿瘤活性及其对免疫功能的影响进行研究．实验过程及部分结果如下：

（注：T细胞转化值越大，T细胞增殖能力越强；+表示进行，﹣表示不进行）

①实验结果表明，刺参匀浆能够____ （填“增强”或“减弱”）机体的免疫功能，在正常机体内免疫系统除防卫功能外，还具有____ 功能．

②设置A组的作用是____ ．要综合评价刺参对免疫功能的影响，除表中的指标外，还可测定____ （写出一项即可）等指标．

语法填空

    Learning any language ____(take) practice － lots of practice! Often, it's difficult to know ____ you should practice it. Should you watch a video? Perhaps,____ would be a good idea to do a few quizzes. Of course, you should try to speak English with your friends. All of these are great ideas, but it's also important to build a routine. A routine will help you make ____ (study) English a habit. That's the best way to improve your English!

    It's important to ____ (expose) to many different areas every day.____, you shouldn't try to study too many ____ (differ) subjects. These suggestions take a 30-minute listening and reading as the basis for daily practice. You are trying to learn many new things, so don't try to learn too much in any one area too ____ (quick)! 

    Take 5 minutes to write down all the new words you find in your listening and reading exercises. Keep a notebook, and write in the ____ (translate) in your native language. Don't forget to learn grammar for 10 minutes. Try to quickly summarize what you listened to and what you read and speak out loud.

    That's it! Approximately 45 minutes a day, every day or at least four times a week! If you continue to do this, you will be ____ (surprise) at how quickly your English improves!