如图，四棱锥P﹣ABCD的底面是直角梯形，AB∥CD，AB⊥AD，△PAB和△PAD是两个边长为2的正三角形，DC=4，O为BD的中点，E为PA的中点．

（Ⅰ）求证：PO⊥平面ABCD；

（Ⅱ）求证：OE∥平面PDC；

（Ⅲ）求面PAD与面PBC所成角的大小．

阅读下列材料，回答问题。

材料一：大多数文艺复兴时期的艺术和问下关注的中心都是人——文艺复兴时期的新人，他或她是自身命运的塑造者，而不是超自然力量的玩物。人们不需要专心于超自然的力量，相反，生活的目的是为了自身所固有的潜能。——斯塔夫里阿诺斯《全球通史》

材料二：

Ben. Sara, Dave, Grace和Alice希望度过一个愉快而充实的周末。请仔细阅读46. 50题中5个人的情况, 从A—F六个地方中, 选出他们可能最感兴趣的场所, 并将字母编号填写在答题位置上。(其中一项为多余选项)

    ____ Ben is a student. He is not good at English, so he wants to buy some books to help him learn English.

    ____ Sara likes hand making. She plans to make some special Christmas cards for her friends.

    ____ Dave likes doing sports and he can play table tennis very well. He also likes watching sports games·

    ____ Grace wants to buy a beautiful dress and a pair of nice shoes for the New Year Party. She also needs a new chair.

    ____ Alice often goes to see movies with her friends. She likes American movies best because these movies are often very exciting and fun.

A. Silver Screen(It's a big and new cinema. Some famous American movies are going to be on this weekend. )

B. Fun Centre(People can play sports as well as watch games there. There will be two table tennis matches this weekend and the price of the ticket is not so expensive. )

C. City Lights Bookstore(There are many kinds of books, magazines and CDs in the shop. You can always find your favorite ones to enjoy. )

D. DIY Workshop(It's a good place for people who like making small things with paper. You can make beautiful lanterns, cards, paper flowers and more. )

E. City Museum (It's a big and famous museum with a long history. If you want to know more about the history of the city, this place will be great. )

F. MIXC Mall (it's a big shopping centre with nearly everything, clothes, shoes, bags, and even furniture·)

    When I was a teenager growing up in Russia, I wanted to leave school and have my own life. The only way I could do this was to work in the local brick factory in my town, or get married. I was nervous when I told my father I wanted to leave school. I thought he would say, "No! You are going to college." He took me by surprise when he said, “OK. We'll go to the brick factory.”
    Two days later, he took me to the factory. I had a very romantic idea of working in a factory. I had imagined everyone to be friends working together and having fun. I even imagined there would be music and singing. I guess I had watched too many movies as a teenager.
    When we arrived at the factory gate, my father spoke to the guard and one minute later we were inside. My father said, “Take your time. Look around.” I walked around the factory looking at the building, the workers, and listening to the noise. It was horrible. I ran back to my father and said, “I want to go home.”
    He asked me, “What do you think of the factory?”
    "It's terrible," I replied.
    "And marriage is even worse!" he said.
    I went back to school the next day thinking about studying hard so I could get into a good college. I enjoyed studying English so I decided to major in languages at college. Thanks to my father and our trip to the brick factory, I now work at the United Nations and my father is very proud of me. I married a very good man and my life is much better than it would have been working in the factory!

His story about ghost (幽灵) made us ________.