下列能正确表示食物链的是（ ）
A．青蛙→螟虫→水稻
B．水稻→螟虫→青蛙
C．大鱼→小鱼→虾米
D．虾米→小鱼→大鱼
由食物链的定义可以知道：食物链的起点是生产者，终点是消费者，中间用箭头来表示，箭头指向吃的一方，而且它们之间存在吃与被吃的逻辑关系，可以判断：
A、起点是青蛙，为动物属于消费者，不是生产者，终点是水稻，为植物属于生产者，不是消费者，为错误项．
B、起点是草，属于生产者，终点是狼，属于消费者，而且它们之间存在吃与被吃的逻辑关系，所以是正确选项．
C、D、大鱼、小鱼和虾米都是动物，为消费者，缺少生产者，无法构成食物链，为错误项．
故选：B
| 阅读下面材料，从每题所给的三个选项（A、B和C）中，选出最佳选项。 | ||
| ||
| 1. Oliver is unhappy because ______. | ||
[ ] | ||
| A. Emma doesn't answer his question B. he has a problem during the adventure holiday C. he doesn't like the adventure | ||
| 2. The girls in the group make Oliver unhappy by ______. | ||
[ ] | ||
| A. laughing at him all the time B. asking him to leave the centre C. calling him bad names | ||
| 3. Emma gives Oliver ______ piece(s) of advice. | ||
[ ] | ||
| A. one B. two C. three | ||
| 4. Emma advises Oliver to ______. | ||
[ ] | ||
| A. leave the centre B. teach the girls a lesson C. tell one of the girls his real feelings | ||
| 5. Which of the following is TRUE to the passage? | ||
[ ] | ||
| A. Oliver is from London. B. Oliver solves his problem by himself. C. Oliver is the only boy in his group. |
缺失，口腔余牙均健康。
关系正常。预行固定义齿修复，正确的设计是（）
为基牙的复合固定义齿修复
为基牙的复合固定义齿修复
为基牙的复合固定义齿修复
为基牙的复合固定义齿修复