如图，直线l₁∥l₂∥l₃，直线AC分别交l₁、l₂、l₃于点A、B、C；过点B的直线DE分别交l₁、l₃于点D、E．若AB=2，BC=4，BD=1.5，则线段BE的长为____．

下列加横线字读音完全正确的一组是(    )。

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    Fear may be felt in the heart as well as in the head, according to a study that has found a link between the cycles of a beating heart and the chance of someone feeling fear.

    Tests on healthy volunteers found that they were more likely to feel a sense of fear at the moment when their hearts are contracting（收缩）and pumping blood around their bodies, compared with the point when the heartbeat is relaxed. Scientists say the results suggest that the heart is able to influence how the brain responds to a fearful event, depending on which point it is at in its regular cycle of contraction and relaxation.

    Sarah Garfinkel at the Brighton and Sussex Medical School said: “Our study shows for the first time that the way in which we deal with fear is different depending on when we see fearful pictures in relation to our heart.”

    The study tested 20 healthy volunteers on their reactions to fear as they were shown pictures of fearful faces. Dr Garfinkel said, “The study showed that fearful faces are better noticed when the heart is pumping than when it is relaxed. Thus our hearts can also affect what we see and what we don't see and guide whether we see fear.”

    To further understand this relationship, the scientists also used a brain scanner（扫描仪）to show how the brain influences the way the heart changes a person's feeling of fear.

    “We have found an important mechanism by which the heart and brain ‘speak' to each other to change our feelings and reduce fear,” Dr Garfinkel said.

    “We hope that by increasing our understanding about how fear is dealt with and ways that it could be reduced, we may be able to develop more successful treatments for anxiety disorders, and also for those who may be suffering from serious stress disorder.”

    A thousand years ago, Hong Kong was covered by a thick forest. As more and more people came to 1 in Hong Kong, these trees were cut down and burnt. Now there is 2 forest left, though there are still some small areas covered with trees. We call these woods, not forests.

    Elephants,tigers and many 3 animals were living in the thick forest. When people came to live in Hong Kong, the 4 began to die out. Early farmers grew rice and kept pigs and chickens in the valleys (山谷). They cut down the trees and burnt them. They needed fire to keep themselves 5 in winter, to cook their food and to keep away the dangerous animals. Elephants 6 disappeared because there was not enough food for them. So did most of the wolves and tigers. Monkeys and many other animals soon died 7 the same way.

    You might think that there are no longer any animals in Hong Kong except in the zoos. There  8 still about 36 different animals living there. One of the most interesting of Hong Kong's animals is the barking deer (麂). These are beautiful little animals with a rich brown coat and a white patch(补丁) under the tail. They look like deer but they are much smaller. They are less than two feet  9 . They make a noise rather like a dog barking. In Hong Kong the barking deer has only one real enemy – 10 . People hunt these little animals though it is illegal (违法的). There are now not many barking deer left. So it is important for people to protect wild animals.

①∃x∈R，2^x＞3^x；②“x≠3”是“|x|≠3”成立的充分条件；③空间中若直线l若平行于平面α，则α内所有直线均与l是异面直线；④空间中有三个角是直角的四边形不一定是平面图形．