1. I have a soccer ball, but I don’t have a volleyball.

2. I have a ping-pong bat, but I don’t have a baseball bat.

3. Li Lei has a basketball, but he doesn’t have a soccer ball.

4. Li Lei has a volleyball, but he doesn’t have a ping-pong ball.

写作指导：1. but可连接两个意思相反的句子，表示转折关系，but前句子加逗号。2. 注意谓语动词的数与主语的人称和数相一致。