IX. Read the text and fill in one word which best fits each gap.
One of the (1) __________ in global warming is carbon monoxide. The more carbon monoxide in the atmosphere, the (2) _________ the atmosphere is able to clean itself. The result is a warming of the atmosphere, the so-called global warming, and possibly ozone damage.
Earlier, it was found that carbon monoxide was concentrated in the Southern Hemisphere, and could (3) _________ attributed to deforestation. Huge areas of forest and grasslands in South America and Africa have been burned, putting carbon monoxide into the (4) __________. Recently, (5) __________, the Southern Hemisphere has been found to be clean, while the Northern Hemisphere is more polluted than expected.
The latest research was (6) __________ during the northern winter. The high levels in the Northern Hemisphere could be because of this. In winter carbon monoxide is destroyed more slowly. There are (7) ________ more fires burned in winter, and possibly industrial processes work harder. It could also reflect the ever-increasing (8) _________ of cars on the roads. Optimists hope that the reason (9) ________ the North