Qian Xuesen was born in Hangzhou, Zhejiang Province on December 11,1911. After his graduation from Shanghai Jiao Tong University in 1934, he ____(旅行) across the Pacific Ocean to the United States for further study. There he received his degrees. After he graduated, he became a teacher as well as a researcher. He worked ____(努力地) and became a famous scientist.

    He ____(返回) to China in 1955. He played an important role in science in China. He was honored as “The Father of China's Missiles(导弹)”. He is the  ____(骄傲) of the Chinese people. He died on ____(十月) 31, 2009 at the age of 98, but he is a man who ____ (仍然)encourages Chinese young people. His love to his country was expressed in his saying, “My career(事业), my ____(成功) is in China and my destination is in China!” When someone said he could make much more money if he stayed in ____ (美国), he laughed and said, “My family name is Qian, but I don't like qian.”

（Ⅰ）求椭圆E的方程；

（Ⅱ）判断▱ABCD能否为菱形，并说明理由．

（Ⅲ）当▱ABCD的面积取到最大值时，判断▱ABCD的形状，并求出其最大值．

浸在液体里的物体要受到液体对它的浮力的作用，那么，浮力是如何产生的呢？

物理上研究问题往往从最简单的问题入手．设想有一个边长为L的正方体浸没在密度是ρ的液体中，如图所示．由于前后两侧面（左右两侧面）在液体中的深度相等，受到的液体的压强也相等，因此受到的压力相等，作用效果相互抵消．而上下两表面却不同：上表面受到的液体压强为p_上=____ ，受到的压力为F_上=____ 　；

下表面受到的液体压强为p_下=____ ，受到的压力为F_下=____ ．因此液体会对正方体产生一个向上的和向下的压力的差F_差=____ ．实际上，这个压力差就是液体对正方体的浮力．