21. Many modern skyscrapers, though visually pleasing, they have heating and cooling systems that require closed windows and consequently waste energy.
(A)visually pleasing (B) they have (C)closed (D)waste
Ⅱ.在可承受地點行走宿營Travel and Camp on Durable SurfacesⅢ.適當處理垃圾維護環境Dispose of Waste ProperlyⅣ.保持環境原有的風貌Leave What You FindⅤ.減低用火對環境的衝擊Minimize Use and Impact from FiresⅥ.尊重野生動植物Respect WildlifeⅦ.考量其他的使用者Be Considerate of Other Visitors
27. Across Europe, there are about 400 of the new energy plants that burn thousands of metric tons of household garbage and industrial waste round the clock and, all the while, ___________ the trash into heat and electricity.
(A) converting (B) convert (C) converted (D) to convert