听下面一段独白，请根据题目要求，从所听到的内容中获取必要的信息，填入答题卡标号为16~20的空格中。听录音前，你将有10秒钟的阅题时间，录音读两遍。你将有60秒钟的作答时间。
Zoos
Functions of zoos
1. Zoos are places of (16)
2. Research into animal (17)has increased our knowledge of zoology, genetics and psychology.
3. Zoos can protect the future of many (18)of animals.
Cruelty of zoos1.Animals are (19)and depressed living in zoos.
2. Frequent contact with human visitors makes animals stresseD、
Essence of zoos1. Zoos have been improved to be good environments.
2. Zoos have more advantages than disadvantages.
3. In an ideal world, zoos would not be necessary with no animals hunted for (20) or environment destroyed