如图，在棱形中，，对角线，若过点作，垂足为，则的长为（ ）

    New rules and behavior standards (行为规范) for middle school students came out in March. ①Who are the most excellent students? ②Middle schools use a new way to decide that. The best students won't only have good grades. They will also be kids who don't dye their hair, smoke or drink. The following are some of the new rules.
    ◆ ③ ______.
    Have you ever copied others' work in an exam? Don't do it again. That's not what an honest student should do. If you have played computer games for two hours in your room, don't tell your parents you have done your homework.
    ◆ Do more at school. ④好学生热爱动物，关心他人。 April is Bird-Loving Month in China. Is your school doing anything to celebrate it? You should join! That way, you can learn more about animals and leam to protect them. And when your classmates are in trouble, remember to give them a hand. You know a friend in need is a friend indeed.
    ◆ Use the Internet carefully. Try to ⑤ ______ away from Web pages that are bad for you. Find good Web sites and use them for homework.
    ◆ Be open to new ideas. Have you ever thought that people could live on the moon? Maybe you can discover a new planet someday. Don't look down on new ideas. ⑥You should welcome them. because new ideas make life better for everyone.

巴西森林资源丰富，对全球气候影响较大，全世界都希望巴西重点保护的自然环境因素是（    ）

2014年2月8日，我国南极泰山站正式建成开站，这是继长城站、中山站和昆仑站之后我国在南极建成的第四个南极科考站，下图为中国南极科考站分布示意图，完成下列问题。

某区10名学生参加市级听写大赛，他们得分情况如下表：

人数
分数

如图，以的一边为直径作，与边的交点恰好为的中点，过点作的切线交于点.
（1）求证：；
（2）若，求的值.

    当前我国政府倡导节约，抵制浪费。作为中学生我们应如何做到节粮、节水、节电呢？请根据以下要求和提示写一篇题为 “How to save”的短文。
提示：
    (1) 节约用水、用电、用纸；
    (2) 去超市自备购物袋；
    (3) 不要浪费食物，乱倒剩饭剩菜；
    (4) 步行或骑自行车上学。
提示词：tap（水龙头），uneaten food（剩余饭菜），electricity（电）
要求：
    1) 80词左右；开头和结尾已给出，不计入总词数；
    2) 文中不要出现作者本人的真实校名和姓名；
    3) 请不要逐句翻译，可适当发挥。

先化简，再求值:，其中，．

珍爱地球，从我做起，回答（1）~（2）题。