Ann is my classmate. She comes from New York, and she lives in Shanghai with her parents now. Every morning, she goes to KFC to have breakfast. Sometimes she buys a hamburger for me. She can't speak Chinese well. In the evening, her father often helps her with it. He's a teacher in our school. He can speak Chinese very well.

    Ann thinks the school life(生活)in China is very interesting. Ann likes reading Chinese books because she wants to know more about China. She tries(努力)to talk with her Chinese friends in Chinese. She hopes to speak Chinese well. She is very happy to live in China. She loves people here.

函数y=3^x与y=3^﹣x的图象关于下列哪种图形对称（   ）

读图，回答下列问题．

“胃肠感冒”在医学上又称“呕吐性上感”，主要是由一种叫“柯萨奇”的病毒引起的，同时伴有细菌性混合感染．它的发病症状主要是：呕吐、腹泻、发热等．

（1）胃部因病菌或其他毒性物质进入，通过非条件反射导致胃体肌肉收缩，将胃内容物排出体外，该反射弧中效应器由____ 组成．神经冲动在离体神经纤维上以局部电流的方式双向传导，但在上述反射弧中，传导方向是单向的，总是由胞体传向____ ．剧烈而频繁的呕吐引起大量消化液的丧失，造成水分大量流失，使机体的内环境渗透压升高，下丘脑的____ 会感知此变化，并促使下丘脑合成和分泌____，作用与肾小管和集合管，促进原尿中水分的重吸收，维持内环境的稳定．

（2）当体内有炎症时会出现发热现象，这有利于吞噬细胞和杀菌物质等转移到炎症区，抵御病原体的攻击，此过程属于机体免疫系统的第____ 道防线．在体温升高的过程中，机体产热量____（填“大于”、“小于”或“等于”）散热量．

（3）机体感染柯萨奇病毒后，通过____ 免疫产生抗体与病毒发生特异性结合．有人提议注射疫苗预防该疾病，注射疫苗预防疾病的机理主要是使机体产生____，提高机体的免疫能力．免疫调节不仅积极应对外来抗原的入侵，同时也随时应对体内的衰老和癌变的细胞，这说明免疫系统具有____ 功能．