把一副三角板如图甲放置，其中∠ACB=∠DEC=90$°$，∠A=45$°$，∠D=30$°$，斜边AB=6，DC=7，，把三角板DCE绕着点C顺时针旋转15$°$得到△D₁CE₁（如图乙），此时AB与CD₁交于点O，则线段AD₁的长度为（     ）

山脉往往成为我国省级行政单位的天然界线，如图所示的界线是（　　）

将某植物放置在黑暗处一昼夜后，选取一叶片按图甲处理，照光几小时后，摘下叶片，去掉锡箔，经脱色、漂洗再碘液处理，结果如图乙所示．下列分析中错误的是（　　）

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　　Mrs. Green is the mother of two children. She is a shop assistant(店员). She is very busy every day. Every morning, she cooks breakfast for her family. She cooks eggs for her daughter and makes bread for her son. At noon she eats hamburgers in her shop. Her children have lunch in the school dining hall.

    In the evening, Mrs. Green gets home very late. When she gets home, her children get ready for dinner. Mr. Green cooks beef noodles for his daughter and cooks carrots for his son. And Mrs. Green usually buys some chicken from the supermarket. It's Mrs. Green's favourite food.

图中属于热带沙漠地区的景观图是（　　）