题目

阅读理解 请认真阅读下列材料，然后从每小题所给的A、B、C、D选项四个选项中，选出最佳选项。     Jay Chou was born on January 18, 1979, in Taiwan, China．He grew up with his mother, and was a quiet and shy kid. He didn’t do well in study, so people thought he would never be successful in life.     As a small child, Jay took a great interest in music. His mother sent him to learn the piano when he was only three years old. He loved it and kept on practicing. When he was in high school, he could play the piano quite well. At the same time, he s如图，在直角梯形ABCD中，AD∥BC，∠A=90°，BD⊥DC，BC=10cm，CD=6cm．在线段BC、CD上有动点F、E，点F以每秒2cm的速度，在线段BC上从点B向点C匀速运动；同时点E以每秒1cm的速度，在线段CD上从点C向点D匀速运动．当点F到达点C时，点E同时停止运动．设点F运动的时间为t（秒）．（1）求AD的长；（2）设四边形BFED的面积为y，求y 关于t的函数关系式，并写出函数自变量取值范围；（3）点F、E在运动过程中，如△CEF与△BDC相似，求线段BF的长．（4）以BF为半径的圆B与以DE为半径的圆D如果相切，直接写出t的值．