已知α，β为锐角，若sinα= $\frac{4}{5}$ ，cosβ= $\frac{5}{13}$ ，则sin2α=____，cos（α+β）=____．

阅读面的材料，根据要求写一篇不少于800字的文章。
    一场名为“ALS冰桶挑战赛”的活动，正在互联网线上线下如火如荼地进行。活动规则极为简单，挑战者要么在24小时内向美国ALS(肌肉萎缩性侧面硬化病， 俗称“渐冻病症”)公益协会捐出100美元，要么往自己头上浇一桶冰水，并录下视频上传至网络，同时还可以向自己的3个朋友发起挑战。借助于社交网络的力量，“冰桶挑战”迅速传播。吸引了美国各界名人如Facebook创始人扎克伯格、微软创始人比尔·盖茨甚至总统奥巴马等人参加，创下了在两周内收到近400万美元捐款的记录。
    “冰桶挑战赛”也传递到了中国，短短四天，国内主要受捐方就获捐200多万人民币。这项公益游戏，也正成为中国科技、财富和娱乐界的头号时尚，雷军、郭台铭、章子怡等相继“履约湿身”，并精心上传了自己被浇冰水那一刻的视频或照片，一时间引来看客无数。
    这个活动旨在用游戏的方式把公众关注的焦点引到罕见病上，进而为罕见病公益事业做点什么，但与以往不同的是，这种慈善捐款的方式没有诉苦，没有眼泪，很多人给予了“有创意”“很欣赏”的评价。不过，其中不少人也会在上述评价过后，再补上一个“但是”，质疑声音主要聚焦于把慈善变成了作秀、炒作意义大于实际意义，甚至有人认为冰桶挑战是一项浪费水资源的行为，与环保理念和公益理念截然相反。
    要求：选好角度，确定立意，明确文体，自拟标题；不要脱离材料内容及含意的范围作文。不要套作，不得抄袭。

任务型阅读

    The twenty first century is really fast and forces us to move faster with the pace(步伐) of it. The smartest way to shop nowadays is online shopping.

    Online shopping saves our precious time. It frees us from unpleasant visits to the shops. We don't need to travel long distances under the hot sun or the pouring rain. Just turn on our personal computers and a simple click will bring us into a magic world.

    It is very convenient(方便的) way of shopping because we can choose the product from a large range(范围) and we get to know the new products. We can see almost all products that we need online. There is food for people and pets， clothes， tools， books and magazines， electronic equipment， souvenirs and many others.

    Things in online stores are cheaper than those in big stores. There are always sales and special offers. With so many stores on line， we can take our time to make a comparison(比较) and choose the lowest price. There is also a possibility to pay by check or credit card(信用卡).

    Besides shopping on line， we can conduct(经营) our sales on line too. Is your family considering(考虑) replacing the old television that does not fit in your new home setting? Then why don' t you try to sell through Internet? Yes， even you can sell your products or un-wanted things through online shopping. You don't need to have your own personal e-commerce site. You can sell it through free ad posting sites. You will find plenty.

    With the latest technology， we have the best chance to shop online and feel the pleasure. You haven't tried it yet? Go and get a true online shopping experience now!

维持地表温度，促进地球上大气运动、水循环和生物活动的主要动力来源是（  ） 

下列关于真核细胞中①～④结构与功能的叙述，正确的是（    ）