题目

 —Are these doctors and nurses tired, Mr. Smith?    —Yes. ________. They have been operating on the patient for at least 10 hours. A. They’re exhausted!                B. You must be joking! C. I’m not surprised!                 D. They are really tired of it! 答案：A（2010•株洲）如图，直角△ABC中，∠C=90°，，，点P为边BC上一动点，PD∥AB，PD交AC于点D，连接AP．（1）求AC、BC的长；（2）设PC的长为x，△ADP的面积为y．当x为何值时，y最大，并求出最大值．