题目

对充有氖气的霓红灯管通电，灯管发出红色光。产生这一现象的主要原因  A．电子由激发态向基态跃迁时以光的形式释放能量B．电子由基态向激发态跃迁时吸收除红光以外的光线C．氖原子获得电子后转变成发出红光的物质D．在电流作用下，氖原子与构成灯管的物质反应 答案：A If you want to be an excellent runner like Liu Xiang, you must be in good health and be prepared to _____________ much hard work.    A. go through             B. suffer from      C. look through          D. come across