In agricultural production, as long as the appropriate limit is not exceeded, the yield of crops will be increased with more fertilizer applied; and the yield of crops will be reduced with less fertilizer applied. It can be seen that the amount of fertilizer applied has a close relationship with the yield of crops. Which of the following logical methods is most similar to the above statement? ['There are sounds of gongs, sounds of blows, and sounds of speech. These sound phenomena are accompanied by the vibration of the air on the object, so it can be concluded that the vibration of the air on the object is the cause of the sound.', 'When sawing with a saw, the saw will generate heat; when filing with a file, the file will also generate heat; when sharpening a knife on a stone, the knife will generate heat; when shooting with a gun, the barrel will also become hot. Therefore, friction can generate heat.', 'The bell is energized by energizing in a glass cover with air. As the amount of air drawn changes, the ring tone becomes smaller and smaller. If the air is completely drawn out, the ring tone will not be heard at all. Therefore, how much air is the reason why the sound is loud, and whether there is air is the reason why the bell can be heard.', 'Cotton is a plant fibre, loose and porous, and can keep warm; snow is frozen by water, with 40% to 50% of the gap, and it is also loose and porous, and can keep warm. It can be seen that loose and porous is the reason for heat preservation.']