阅读短文，从短文下面方框中的六个句子中选择五个还原到短文中，使短文通顺完整、衔接自然．

    In Australia there is a famous island called Fraser Island．A great many visitors come here for holidays every year．Why？The reason is that it is special．____．In fact，it is the largest sand island in the world．It's about 200 kilometers long and 240 kilometers wide．

    Though the island is a popular place of interest，there is no airport on the island．The long beach along the east coast works as the airport．____．

    On the island there are sand hills without any plants，but there are forests with old trees，beautiful flowers and over a hundred lakes，too．____．

    Every year，visitors come to enjoy the island's natural beauty．People like camping and hiking there．____．Animals were killed for food and this made them in danger of extinction （灭绝）．They threw rubbish everywhere，and the lakes were seriously polluted．

    ____．Rules have been set up．For example，visitors are not allowed to use motorboats （摩托艇） or go fishing in the lakes，and they mustn't leave any rubbish．

A．Planes arrive and leave from here

B．Anyone who breaks the rules w il be pun i shed

C．The island s completely made of sand

D．Unluckily，visitors have caused many problems

E．Many kinds of birds and animals live in the forest

F．So it is time to protect the environment of the island．

已知向量$\overrightarrow{a}$=(2,1),$\overrightarrow{b}$=(3,λ)，若$\overrightarrow{a}$$\perp$$\overrightarrow{b}$，则λ=____ 

下图历史现象出现的主要原因是（    ）

有关人士提出的公式“7+1>8”揭示了体育锻炼与学习效果之间的辩证关系。在实施素质教育的今天，学习之余进行适当体育活动，可以调节情绪、陶冶情操、完善人格、提高社会适应能力和创造能力。这个公式旨在说明（   ）