1. 3 -> The three major ways are water, land and air pollution
2. A -> The polluted water can cause cholera and typhoid fever
3. cho hỏi 'it' chỗ nào :v
4. B -> It is often caused by human activities such as careless disposal of wastes, over-mining of minerals and wrong use of land for planting
5. D -> This happens through the release of carbon monoxide gas from exhaust pipes of motor vehicles