题目

 Smoking too much can cause health problems，so any heavy smoker may find himself________ in the long run. A．at risk                  B．in need              C．in return              D．at ease 答案：A（2006•临沂）如图，在Rt△ABC中，AC=5，BC=12，⊙O分别与边AB，AC相切，切点分别为E，C，则⊙O的半径是（ ）A．B．C．D．