1、一个主语加几个并列的谓语: He went up to the door,opened it and entered. You may stay here or leave. I wanted to help them but couldn't. 特殊并列: He went down the hill,through the street and into a small house by the road side. 【省略了重复的谓语动词went,而将went后面连接的几个介词直接并列】 2、两个对象并列,正式表达,可以根据句子意思选用and,but,or,otherwise 等,直接用逗号也有,但不算正规表达. Use your head and you will have a good idea. Come to school on time,or you will be punished. 3、He is 8 years old and is playing football 严格按照语法来看,这句话有明显的问题: ①时态不一致:并列、平行结构,要使用对等词形(包括时态) ②两个并列部分意义表达上不通畅: He is (only)8 years old but can play football well. or He is 8 years old and plays football well. 祝你开心如意!