在一片湿润的土地上，有一堆长满苔藓的腐木，其中聚集着蚂蚁、蚯蚓、蜘蛛、老鼠等动物．这些生物与其生活的环境相互影响、相互作用，共同构成了一个（　　）

阅读短文，然后根据其内容从A、B、C、D中选出最佳选项。

Mr Li: Sam, did you enjoy your first Spring Festival in China?

Sam: Yes, I did. During this festival, many family members get together.

Mr Li: Yes. I hear that at Thanksgiving Americans also get together for a special meal. It sounds similar.

Sam: Yes. It's similar. During these holidays, both the Chinese and Americans come home and have a big dinner. It's great fun.

Mr Li: What do you think are the main differences between the Spring Festival and Thanksgiving?

Sam: Well, we take part in different activities and eat different kinds of food. In China, people usually set off fireworks and eat dumplings. In the US, we usually watch a Thanksgiving parade and an American football game on TV. We also eat turkey.

Mr Li: That's interesting.

“朴雪”乳酸亚铁口服液可以有效地治疗人类缺铁性贫血症，这是因为其中的Fe²⁺进入人体后能（　　）

门阀制是从汉到隋唐最为显著的官员选拔制度，选成朝廷重要的官职往往被少数世家大族所垄断，个人出身对于其仕途的影响远大于其本身的才能与专长。这种现象（    ）

蜂群中蜂王、工蜂、雄蜂各司其职，分工协作。蜜蜂这种行为属于____ 行为。