C. heat goes down if temperature is raised

D. heat increases the temperature of rocks

27. What does the author intend to tell us?

　A. people will no longer consider building materials in the future

B. energy-saving buildings will become more popular in the future

　C. almost all people will move into the houses heated by large rocks

　D. energy engineers will devote themselves only to modern technology

C

　　Many cities and towns have laws that require people to recycle paper and plastics. Now some state and local governments have passed laws that require citizens to recycle their food waste as well. California and Vermont have statewide laws about recycling food waste that apply to businesses and homes. The process of recycling food waste and turning it into usable soil is called composting(堆制肥料).

　　Food waste that can be composted includes fruit and vegetable peels, coffee grounds, tea bags, and eggshells. Garden waste such as stems and leaves can also be composted. Meat, fish, and dairy food waste cannot be recycled.

　　According to environmental groups, composting reduces the amount of trash going into landfills(垃圾填埋池), and composted waste holds a wide range of nutrients. When compost is added to the soil in gardens and fields, it helps crops grow.

　　Reducing the amount of waste that goes into landfills is one reason why cities and states are passing food-waste recycling laws. "Our landfills are far from enough for the creation of new ones is shrinking." Renee Crowley, a project manager said.

　　Officials in Seattle, Washington, say that food waste makes up 30% of the trash going into landfills, and they are looking to reduce that percentage. That city has a law requiring people to recycle food waste. It is banned from all garbage. There is a fine for people who put it into regular garbage.

　　Crowley points out that even in cities where food recycling is not a law, there are often places where citizens can drop off their food waste for composting. Many schools and colleges have also started composting programs.

　　Those who are against food-recycling laws say that the composting process is costly. In addition, it can be difficult for people who live in apartments to store their waste because they don't have access to outside storage bins. Patti Ferguson from Orange County, California, told her local newspaper that she thought an indoor container containing food waste would get smelly.

28. What do we know about composting from the text?

A. It is cheap to compost food waste

B. Not all food waste can be reused

C. Not all soil can be composted

D. It is usually processed in empty landfills

29. What is the third paragraph mainly about?

A. Ways of keeping nutrients in the soil

B. Ways of reducing the amount of trash

C. Benefits of recycling food waste

D. Examples of different useful nutrients

30. In Seattle, throwing food waste into garbage is .