新生儿生理性胎黄有何特点？
参考答案：
新生儿生后2-3天出现黄疸，4-7天最明显，足月儿10-14天消退，早产儿可延迟至3-4周消退.
一束激光射到平面镜上，当入射光线与镜面夹角为20°时，反射角为______°，当入射角是25°时，反射角为______°，反射光线和入射光线之间的夹角是______°，如果光线垂直入射，则反射角为______°．
To ______ the other players, the athlete ________ a lot of difficulties in his training.
A．win; defeated
B．defeat; overcame
C．beat; defeated
D．win; overcame
