同学们喜欢的油炸食品，含有一种叫“丙烯醛”（化学式C3H4O）的有毒物质．下列关于丙烯醛的说法正确的是（ ）
A．丙烯醛由三种原子组成
B．丙烯醛由碳氢氧三种元素组成的
C．丙烯醛中碳氢氧元素的质量比3：4：1
D．丙烯醛中含有四个氢原子
A、丙烯醛由三种元素组成，不能说丙烯醛由三种原子组成．故选项错误；
B、丙烯醛由碳氢氧三种元素组成的．故选项正确；
C、丙烯醛中碳氢氧元素的质量比为：9：1：4．故选项错误；
D、应该说1个丙烯醛分子中含有四个氢原子．故选项错误．
故选B．
| 完形填空。 | |||
| After she did a lot of shopping , Mrs Smith came out of the shop and started to walk to the bus stop. Her bag was so 1 that she had to rest for a few minutes. She stopped 2 a new and bright car. It was just at the side of the road. As she stood there, she saw a policeman 3 towards her. "Excuse me, madam," said the policeman. "Can you 4 that sign over there?" “Yes, I can,” said Mrs Smith. " It 5 'No Parking'. "Yes. madam. So why have you parked your car here? I shall 6 to give you a parking ticket. " "But this isn't my car," said Mrs Smith. "Isn't it?" said the policeman, and his face turned 7 . "I'm very 8 . Still I have to put a ticket on the front of 9 car. "But he was not able to finish writing the ticket because 10 woman had arrived She kissed the policeman and said, "Hello, dear. I knew I could 11 you here at this time of' the day. Happy birthday! I have got a 12 for you. I have 13 you your birthday present. " "Thank you, dear, "said the policeman.”But 14 is it? "His wife pointed at the red car. “Here it is," she said. "But you 15 leave, it on this road for very long. There's a ‘No Parking' sign over there. " | |||
| ( )1. A. beautiful ( )2. A. in ( )3. A. coming ( )4. A. tell ( )5. A. was ( )6. A. ask ( )7. A. red ( )8. A. angry ( )9. A. my ( )10. A. a ( )11. A. catch ( )12. A. ticket ( )13. A. sent ( )14. A. how ( )15. A. needn't | B. expensive B. by B. come B. believe B. says B. clecide B.left B. happy B. your B. another B. find B. cake B. taken B. where B. mustn't | C. heavy C. on C. comes C. look C. spoke C. love C. right C. glad C. the C. other C. get C. thief C. given C. what C. won't | D. important D. under D. came D. read D. wrote D. have D. back D. sorry D. her D. the other D. look for D. surprise D. brought D. which D. shan't |