Read the paragraph carefully. Then respond to the question about the topic sentence, main point, or supporting details. As many landfills run out of space, some communities are making plans and tackling their heaping piles of garbage with innovative solutions. Of the garbage Americans produce every day, only about 30 percent reaches a recycling center. Education about how and what to recycle is costly but essential. Much of the junk we consume and throw out is not designed with recycling in mind. This solid waste creates one of the biggest problems: recyclable material is clogging landfills. In order to extend the lifespan of their landfills, some communities are expanding recycling programs and trying new technologies to turn trash into energy. A few cities are planning new energy plants that burn garbage to produce energy while still producing less pollution than landfills. Several other cities have facilities that use bioreactor landfills to speed up the decomposition process for trash from 100 years to 5–10 years. The costs and pollution generated by landfills force communities to think creatively about what to do with everything we throw out.

Which of the following sentences offers a supporting detail for the main point of the paragraph?

a. Several other cities have facilities that use bioreactor landfills to speed up the decomposition process for trash from 100 years to 5–10 years.

b. Much of the junk we consume and throw out is not designed with recycling in mind.

c. Of the garbage Americans produce every day, only about 30 percent reaches a recycling center.

d. Education about how and what to recycle is costly but essential.