简述队列研究的基本原理及其基本特点
参考答案：
原理：在某一特定人群中选择研究对象，根据目前或过去某个时期是否暴露于某个待研究的危险因素，将研究对象分为暴露组和非暴露组，或按不同的暴露水平将研究对象分为不同的亚组，随访观察一段时间，检查各组人群待研究结局的发生情况，比较各组结局的发生率，从而检验和评价暴露因素和结局的关系.
特点：①在时序上是由前向后的；②属于观察性研究；③研究对象按暴露与否分组；④是从“因”到“果”的研究。
| 阅读理解。 |
| As a large part of land in Hawaii is rocky and mountainous, the state has little space in which to grow crops. Some areas are also covered with hard, black lava (熔岩) on which nothing can grow. Even so, Hawaii produces large quantities of farm products. The volcanic (火山的) soil in the valleys and lowlands is very rich, and the warm climate makes it possible to grow crops all year long. Rainfall is plentiful on the northern and eastern sides of each island. Much of the land on the southern and western sides of each island receives too little rainfall for most crops to grow well, but in many of the places where rainfall is light, wells and mountain streams supply water for irrigation. |
| 1. The main purpose of the passage is to describe the Hawaii _____. |
[ ] |
| Ａ: geography Ｂ: market system Ｃ: farming conditions Ｄ: living conditions |
| 2. Where is most of the farming done in Hawaii? |
[ ] |
| Ａ: Along the coast Ｂ: On the mountain sides Ｃ: On the lava beds Ｄ: In the lowlands |
| 3. When is the Hawaiian growing season? |
[ ] |
| Ａ: Throughout the entire year Ｂ: During all seasons except winter Ｃ: Mainly in the spring and summer Ｄ: Only during the long summer months |
| 4. How do dry areas in Hawaii get their water? |
[ ] |
| Ａ: It is carefully collected when it rains. Ｂ: It is stored in mountain reserviors. Ｃ: It is brought in from other areas. Ｄ: It is provided by wells. |
| 5. Which of the following is right? |
[ ] |
| Ａ: There are quite a few mountains in Hawaii. Ｂ: Hawaii produces large quantities of farm products because of its little plantable space. Ｃ: The soil in Hawaii is very rich everywhere. Ｄ: The climate in Hawaii is warm for its mountain streams. |