A、Make people come up with rough numbers and estimates. B、Make people use less energy and generate fewer gases. C、Help scientist

Climate change is making it harder than usual for scientists to figure out what the future will bring and what impact weather changes will have on society and the economy. A sudden increase of severe weather events has already destroyed homes, businesses and lives. Some fairly simple changes may reduce the toll.
    Wind tunnel tests, done by the Insurance Institute for Business & Home Safety, showed that [20]stronger construction costs a little more, but holds up much better to extreme weather. The growing number of unusually strong storms has convinced people that extreme weather is the "new norm." Extreme weather events have increased in frequency over the past 50 years and are expected to become even more common, more intense, and more costly.
    Drought is another suspected consequence of climate change, and dry ground means more wildfires in California Current mathematical models of climate change do a poor job of predicting the economic impact of drought and other weather events. All we can do is come up with some rough numbers and estimates. Consensus estimates that maybe experts provide, that give us a view of what would the terrible outcome look like if we don’t do anything.
    To help deal with climate problems, policymakers should take actions such as imposing a tax on carbon dioxide emissions. A carbon tax would encourage companies and families to use less energy and generate fewer of the gases thought to be driving changes in the climate.
20 What do we know about stronger construction?
21 What is the consequence of drought in California?
22 What would be the benefit of imposing carbon tax?