A、It is the first study on the subject. B、It is a longitudinal study on the subject. C、It is an incomplete study on the subject.

Even the dirt on the ground is likely making climate change worse, a new study finds.
Scientists studied device readings, soil measurements, plant growth details and satellite observations from around the world. Their work is the most complete study yet on the subject. They found a sharp increase in carbon released into the atmosphere by bacteria and fungi in soil from 1990 through 2014. Researchers explain that the carbon comes from the dead plants and leaves the microbes eat. As temperatures rise, the microbes eat more. And the more they eat, the more carbon they make into carbon dioxide and release into the atmosphere. This uncontrolled cycle speeds up and intensifies climate change, says Jerry Melillo of Marine Biological Laboratory in Massachusetts. Melilo was not part of the study.
Overall, soil releases about nine times more carbon than human-caused activities. But that is part of a natural cycle: The amount of carbon released into the air is about equal to the carbon oceans and plants take in. However, carbon released from fossil fuel causes an imbalance. Burning coal, oil and natural gas puts more carbon into the atmosphere than nature can take out. The additional carbon heats the air and soil. And as the air and soil get hotter, the earth will release yet more carbon that it has been holding. If something isn’t done, “we are really in trouble,” said Rattan Lal of Ohio State University, who wasn’t part of the study. He added that proper soil conservation can help keep more carbon in soil. Conservation methods include avoiding turning the soil, covering off-season crops and leaving crop deposits on the ground.
Questions 19 to 21 are based on the passage you have just heard.
19. What does the speaker say about the new study?
20. What can we learn about carbon release?
21. What does Rattan Lal say at the end of the talk?