(误)She was playing piano.
(正)She was playing the piano.(演奏乐器，如piano，violin，乐器前面要加定冠词the。)
(误)The children go to the school every morning.
(正)The children go to school every morning.(go to school是习惯用语，不加the。)
(误)She has a beautiful hair.
(正)She has beautiful hair.(hair指头发的整体，是不可数名词，前面不加a。)
(误)She likes to watch the TV.
(正)She likes to watch TV.(看电视，习惯上TV前不加the。)
(误)She was listening to radio in the room.
(正)She was listening to the radio in the room.(听广播，习惯上radio前面加the。)
(误)Nile River is the longest river in Egypt.
(正)The Nile River is the longest river in Egypt.(在河流，山脉等名称前要用定冠词。)
