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1. My teacher has not written two books. 
My teacher hasn't written two books. 
2. I have not accepted the offer. 
I haven't accepted the offer. 
3. They have not invented many fun games. 
They haven't invented many fun games. 
4. The light has not attracted all the bugs. 
The light hasn't attracted all the bugs. 
5. Joe and Lynn have not become rich and famous. 
Joe and Lynn haven't become rich and famous. 
6. We have not found that he works very hard. 
We haven't found that he works very hard. 
7. Cassandra has not waited a long time for the news. 
Cassandra hasn't waited a long time for the news.