题目

Christmas is the most important festival in the western world. It   76   (fall) on December 25th. When my mother and I stayed in America, we    77    (invite) by one of my mother’s friends to observe Christmas with an American family. We bought some   78    (present) for our American friends on our way    79    their house. They had prepared different kinds of gifts for their family and guests when we got to their house, such as Christmas candles, cakes, cards, little toys, biscuits and so on. A Christmas tree was placed in     80    corner of the brillia “神州8号”飞船返回舱顺利到达地球后，为了及时将航天员救出，地面指挥中心在返回舱预计到达的区域安排了同一条直线上的三个救援中心(记为B，C，D)．当返回舱距地面1万米的P点时(假定以后垂直下落，并在A点着陆)，C救援中心测得飞船位于其南偏东60°方向，仰角为60°，B救援中心测得飞船位于其南偏西30°方向，仰角为30°，D救援中心测得着陆点A位于其正东方向； (1)求B，C两救援中心间的距离； (2)求D救援中心与着陆点A间的距离．