Answer: Option 1: The digestive systems of ruminants (cows, sheep, etc.).
Step-by-step explanation:
Methane is a greenhouse gas that is 25 times more potent than carbon dioxide at trapping heat in the atmosphere. It is produced by a variety of sources, including:
The digestive systems of ruminants: Ruminants are animals that have a four-chambered stomach. The first chamber, called the rumen, is home to bacteria that ferment plant matter. This fermentation process produces methane gas.
Ruminants digestive system
Rice cultivation: When rice plants are flooded, bacteria in the water produce methane gas.
Rice cultivation
Decaying wetland vegetation: Wetlands are areas of land that are saturated with water. When vegetation in wetlands decays, it produces methane gas.
Decaying wetland vegetation
Natural gas and oil production: Methane is a byproduct of natural gas and oil production.
Coal mining: Methane is also produced during coal mining.
Automobile exhaust does not produce methane gas. It produces carbon dioxide, nitrogen oxides, and other pollutants.
So, the answer is that the digestive systems of ruminants are a significant source of methane emissions. Other significant sources of methane emissions include rice cultivation, decaying wetland vegetation, and natural gas and oil production.