根据句意及首字母提示，补全句中所缺的单词。 1. Look at the s________ of an elephant. It's amazing. 2. We c________ with each other mostly by e-mail. 3. We can learn by e________ that oil and water will not mix. 4. He is f________ with Chinese ancient history. 5. At the entrance of the street there is a 'No E ________' sign. 6. If you paid more a________ in class, you might actually learn something. 7. 'Sit!' he said, and the dog o________ him instantly. 8. The truck s________ up going down the hill. 9. The difference between h________ and animals is that the former one can make tools but the latter one can't. 10. After supper his parents always go d________ to have a walk and Tom goes u________ to do his homework.