单项选择
1. Sustainable development is long-term ______which focuses on the environment and ____ _ natural resources.
A. plan; preserve B. plan; preserving
C. planning; preserving D. planning ;preserve
2. A giant helium(氦) balloon is telling residents of Paris how good or bad the air quality is. When it’s good, the balloon ----measuring 22 meters wide and 32 meters high---shines green. _________, it’s red.
A. Though terrible B. Whenever good C. If worse D. When bad
