I have breakfast every morning 一般
I had breakfast yeasterday 过去
I will have breakfast at 9:00 将来
I have had breakfast already 完成
I am eating breakfast now 现在进行
If we were here,we would have breakfast 虚拟
I were having breakfast during 7:00 to 7:30 yesterday 过去进行
I will have had breakfast by this time tomorrow 将来完成
When my mother came home ,I had alreay eaten my breakfast.过去完成