对比遥感图像发现，今年来我国新增土地最快的黄河三角洲，湿地增加幅度减小。黄河三角洲湿地泥沙来源主要是（    ）

下列各组地形名称中，全部位于北方地区的是（    ）

已知函数f（x）=tan（2x+$\frac{\mathrm{\pi }}{4}$），求f（x）的定义域与最小正周期．

任务型阅读

　　There are some students in front of the lost and found box. The duty monitor Alan is asking some questions.

Alan: Jim, is this your English book?

Jim: No, it isn't.

Alan: Linda, is this your English book?

Linda: Yes, it is. Thanks.

Alan: Gina, what colour is your pencil?

Gina: It's green.

Alan: Is this your pencil?

Gina: Yes, it is. Thank you.

Alan: What is your name?

Jenny: My name is Jenny.

Alan: Is your ruler green or yellow?

Jenny: It's green. There’s my name “Jenny” on it.

Alan: Oh, here you are.

Alan: Here’s a nice bag; whose bag is this?

Paul: Let me see. . .  Oh, it's mine.

Alan: Look at the cute doll. Is this yours, Mary?

Mary: No, it isn't. I think it’s Betty's. Is there a watch in it?

Alan: Sorry, I haven’t seen it so far.

根据对话内容, 完成以下任务。