请根据括号中的中文提示、英文释义或句意，写出句中所缺单词，使句子通顺。
The girl is very healthy because she ___________(很少) eats junk food and exercises more.
The bus is so ___________(拥挤的) that we have to wait for the next one. How unlucky!
Zhou Kehua’s girl friend will be put in __________for five years because she also has done something against the law.
As teachers, we should __________(say again) the important points in class again and again so that some slow students can have a good understanding.
It is our duty to protect the ____________(环境）because pollution is getting more and more serious.