据新华社专电，某癌症研究所的一项最新研究结果显示，频繁接触接触甲醛（HCHO）的人死于血癌、淋巴癌的机率比接触甲醛较少者高出78%。甲醛是一种有机化工原料，常用做医学标本防腐剂。据媒体报道，有少数不法分子为牟取暴利，在水产市场上出售用甲醛溶液浸泡过的带鱼等水产品，严重违反《中华人民共和国食品安全法》，受到有关部门的惩处。试回答下列问题：
（1）甲醛中共含有_________种元素。
（2）甲醛中含碳元素的质量分数为_______。
（3）下列有关说法中，你认为正确的是________（填序号）。
A.甲醛可作食品防腐剂 B.甲醛是营养物质 C.甲醛是调味品 D.甲醛能使人体蛋白质失去生理活性
（1）3
（2）40%
（3）D
| 阅读理解。 |
| George Stephenson was born in 1781 in a poor family. He had to start work when he was only eight. When George was fourteen, he became his father's helper. He spent a lot of time learning about engines (发动机). And on holidays he often made one engine to pieces and studied each piece carefully. Soon he became a very good worker though he could not read or write. He began to learn English letters when he was seventeen years old. Every day after he did twelve hours of hard work,he walked a long way to have lessons from a young school teacher. On his eighteenth birthday, he wrote his own name for the first time in his life. George invented (发明) many things in his life. The train was the greatest one among them. Today when we take trains from one place to another, we'll think of this great man-George Stephenson. |
| 1. In which year did George Stephenson start to help his father? ______. |
[ ] |
| A. In 1781 B. In 1789 C. In 1795 D. In 1798 |
| 2. He learned about the engine ______. |
[ ] |
| A. through reading and writing B. by making it to pieces and studying each piece carefully C. at lessons from a young teacher D. by asking a lot of questions |
| 3. He spent a lot of time learning about engines and soon he became ______. |
[ ] |
| A. a great man B. a good maker C. a good worker D. a good student |
| 4. George Stephenson invented the ______. |
[ ] |
| A. the train B. the telephone C. the car D. the computer |
| 5. From the passage we know George Stephenson was one of the greatest ______ in the world. |
[ ] |
| A. workers B. writers C. learners D. inventors |