C) farmers use mechanical devices to do many tasks
Explanation:
The tasks that farmers used to do manually like threshing, harvesting etc or with the help of animals like ploughing are now being done by them with the help of mechanical devices. Ploughing which was earlier done with the help of bulls is now done with the help of tractors. People involved in threshing, harvesting etc have now been replaced by threshers and harvesters. Tractors, threshers, harvesters etc. are mechanical devices which make farming very easy, fast and are also much efficient, as a result of which productivity has increased manyfold.
As more CO2 (carbon dioxide) is released into the atmosphere, it traps more heat energy from the sun, and slowly warms the average temperature of the earth. This is the simplified version of what global warming is. Carbon dioxide is considered a greenhouse gas.
