单项选择题
The word "smog" has become a household word in urban China. Smog is an 11 of greenhouse gases and pollutants that reduce visibility and harm respiratory functions. Smog is typically 12 cities with high concentrations of cars and factories. The population density, amount of industry and the fuels used 13 together to have an impact on smog levels. During summer, smog is worse 14 the production of ozone, the main component of smog, increases in strong sunlight. The important thing to understand about smog is that this kind of pollution is spread out 15 large distances.
Walking, biking or using public transportation can help limit ozone production. 16 , decreasing household electricity use and keeping your vehicles fuel-efficient reduces 17 greenhouse gases. Checking tire pressure, oil levels, air filters, and getting regular maintenance help 18 fuel efficiency. Be sure to use only the fuel recommended in the vehicle"s user 19 . Simple steps like avoiding stop-and-go traffic and reducing vehicle workload decrease smog-related emissions. To lighten the workload, avoid running the air-conditioner, 20 the engine and carrying heavy objects in the vehicle.
16（）
A.In addition
B.After all
C.By contrast
D.At first
相关考题
- 单项选择题 20（）
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- 单项选择题 17（）
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