如图，已知AB⊥平面ACD，DE⊥平面ACD，三角形ACD是正三角形，且AD=DE=2AB，F是CD的中点．

（1）求证：平面CBE⊥平面CDE；

（2）求二面角C﹣BE﹣F的余弦值．

如图所示为电磁铁和永磁体相互作用产生的磁场，请根据图中磁感线的方向标出永磁体A左端的磁极极性和电磁铁电源的“+”极．

郑州-徐州高铁将于2016年7月1日正式投入运营。图为郑徐高铁线路及周边地区略图。读图，影响郑徐高铁修建的主要因素是（   ）

根据短文内容，用方框中所给单词的适当形式填空，每词限用一次。                                                                                     

    Do you love animals? Would you like to keep animals as a pet? Nowadays, many people like to keep pets at home. The most popular____  are cats and dogs. They are friendly to people, and they are also ____  to take care of. Some people like parrots as pets. Pets lovers will____ lots of things for their pets, such as beds, clothes and even toothbrushes. Pets are very useful, too. The people who can’t hear need the dogs' help to answer the door. And the people who live____  should keep a pet if he wants to be healthier and ____ . If you have pets, don't forget to spend more time with them. They need love, too.