A. Farmers produce the largest amount of soot.

B. Black carbon contributes to burning crop waste and wildfires.

C. Black carbon emissions come from several sources and affect the earth’s temperature.

1. The world’s biggest source of soot is ____________.

A. burning forests

B. burning crop waste

C. killing living things in the soil

2. Black carbon only stays in the atmosphere for a few ____________.

A. hours B. days or weeks C. months

3. Black carbon speeds up _______________.

A. the release of sunlight into the air

B. burning of crop waste

C. ice melting

4. The next part of the talk will probably be about ______________.

A. ways to reduce black carbon emissions

B. heat-trapping gases

C. other heat-trapping pollutants