根据句子意思完成已给出首字母的单词。

1. China has the l___________ population with 1.3 billion.

2. Chen Jun said that Project Hope had c                     his life.

3. Can the homeless people get good food and m____________ treatment?

4. Walking or riding a bike will save energy and r____________ air pollution.

5. Almost everyone knows that air pollution is h____________ to people's health.