长期的阴雨天造成了小麦地中出现了水涝现象，植物则出现了萎焉现象，这其中的主要原因是（　　）

    My name is Tom. I come from England. I like to have friends who are different from me. My best friend is Paul. Paul is funnier, more outgoing and athletic than me. He always tells jokes and makes me laugh. We also like different things. He likes going to the movies. He likes playing sports. He likes pop music. But I like reading books. He often asks me to go to the movies and gives me some interesting books. And I often give him CDs. We often help each other.

生态系统的组成包括（　　）

下图为人体部分血液循环示意图，数字表示人体内的某些结构。请分析回答：