1、主单谓单

①单数可数名词 （主）单（谓） e.g.1 A book is on the desk. ②不可数名词 （主）单（谓） e.g.2 Water is colorless. ③doing,to do,句子 （主）单（谓） e.g.3 Seeing is believing. To see is to believe. What you saw is true. ④复合不定代词 （主）单（谓） e.g.4 Nobody knows his name.