根据句意和首字母及汉语提示完成单词。 1. The s on the teacher's face showed that she was pleased with us. 2.  Listen!There is somebody k at the door. 3. There are n 34 million people living here. 4. Now stop writing and listen to me c . 5. Trees and flowers are planted every year to make our country more b 6. Pollution is a (严重的) problem. Scientists have come up with some good ways to solve it. 7. It is (必要) to learn English well. 8. A lot of meetings were put off because of the (危险的) disease. 9. I (不知道) if the teacher will come tomorrow. 10. Ann has made great (进步) recently.