将下列两个简单句合并成一个含有非限制性定语从句的复合句。
1. I am reading Harry Porter. It is an interesting book. →
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2. He failed in the exam. It made his parents very angry. →
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3. He has two sons. Both of them are doctors. →
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4. Recently I bought an ancient Chinese vase. The price of it was very reasonable. →
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5. Last week, two persons came to see the house. Neither of them wanted to buy it.→
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6. I have lost the pen. My father bought it for my sixteenth birthday. →
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7. Do you see the house? The windows of it face south.→
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8. He must be from Africa. It can be seen from his skin.→
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9. The book is worth reading. He paid 6 yuan for it. →
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10. She is a teacher of much knowledge. Much can be learned from her. →
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