如图，在等腰三角形中，AB=AC，BC=4，D为BC的中点，点E、F在线段AD上，tan∠ABC=3，则阴影部分的面积是____ 

    One of my favourite cartoons are Pleasant Goat and Big Big Wolf. I have seen many cartoons. Because Pleasant Goat and Big Big Wolf is my favourite. I like it because it's much modern than another cartoons. The story is about a clever goat. It is the hero of the story. It's clever and brave. It always finds ways help other goats run away from Big Big Wolf. It leads other goats fighting the Big Big Wolf. They protect each other and work hardly together and they are always successful. The cartoon is very interested. I can't always help to laugh. If you haven't saw it yet, please don't miss it. 

人血红蛋白由两条α链和两条β链构成。镰刀型细胞贫血症患者的β链第6位的谷氨酸替换为缬氨酸导致血红蛋白聚集为纤维状，红细胞形状随之改变。下列叙述错误的是

①小强考试抄小抄，没有被老师发现

②小华负气离开家，把躲藏的地点告知好朋友小云。并要求保密，小云及时转告小华的父母

③学生会干部小刘在检查卫生时，为了让自己班级不被扣分，悄悄地把地上的纸屑踩在脚下

④数学科代表小秦没有做数学作业，可是在不交作业的名单上却没有自己的名字

⑤小明为了父母高兴，涂改了考试成绩

⑥虽然天下雨了，但小燕还是按约定去帮助同学辅导功课

⑦小金承诺不将同学上网的事情告诉老师

⑧大家约好周日排节目，梅梅却为了过生日没有参加排练

世界上最大的黄土堆积区是（    ）