Many people believe that poverty is only a problem in rural areas. __, it is also a problem in some urban areas.
30. The coal we use today should _____ plants and trees.
29. That's all for the party. Let's _____.
28. They ____ friends since they met in Shanghai ten years ago.
27. When he heard the news, his heart ______ very fast.
26. The old woman could not _____ the terrible noise, and she had to close the door and windows.