The correct answer is option 1, CFC emission. CFCs, or chlorofluorocarbons, are potent greenhouse gases that were commonly used in aerosol propellants, refrigerants, and foam-blowing agents. However, they are not a significant cause of present global warming and climate change.

Option 2, carbon dioxide emission, is a major contributor to global warming. Carbon dioxide is released into the atmosphere through the burning of fossil fuels and deforestation. It is a greenhouse gas that traps heat from the sun, leading to an increase in the Earth`s temperature.

Option 3, deforestation, is also a key factor in global warming and climate change. Trees play a crucial role in mitigating climate change by absorbing carbon dioxide during photosynthesis. When forests are cleared or burned, the stored carbon is released back into the atmosphere, contributing to the greenhouse effect.

Option 4, methane emission, is another significant cause of global warming. Methane is released during the production and transport of coal, oil, and natural gas. It is also emitted by livestock and other agricultural practices. Methane is a potent greenhouse gas, capable of trapping more heat than carbon dioxide over a shorter period.

In summary, while options 2,