题目内容：

阅读下列短文，根据短文内容填空。在未给提示词的空白处仅填写1个适当的单词，在给出提示词的空白处用括号内所给词的正确形式填空。

The animals 1. (keep) together in small spaces, with no privacy and little opportunity2. mental and physical exercise. This results in unusual and self-destructive behavior 3. (call) zoochosis. A worldwide study of zoos found that zoochosis is common among animals kept in small spaces or cages. Another study showed that elephants spend 22 percent of their time making repeated head movements or biting cage bars, and bears spend 30 percent of their time 4. (walk) back and forth, a sign of unhappiness and pain.