| 1 | Malaria is an ancient and persistent disease. | |
| 2 | Manchester has social blights of its own. | |
| 3 | Waste disposal is one of the biggest headaches for cities. | |
| 4 | The country's intractable political problems are contributing to the problem. | |
| 5 | Electric bikes were once touted as a solution to China' s transportation woes. |