The correct answer is: A. Higher than at present.
The greenhouse effect is a natural process that warms the Earth’s surface. Without it, the average surface temperature of Earth would be about -18 degrees Celsius (0 degrees Fahrenheit), too cold for liquid water to exist on the surface. The greenhouse effect is caused by greenhouse gases, such as water vapor, carbon dioxide, methane, and ozone, which trap energy in the atmosphere. This trapped energy warms the planet.
The greenhouse effect is essential for life on Earth. Without it, the Earth would be a frozen wasteland. However, human activities are increasing the amount of greenhouse gases in the atmosphere, which is causing the planet to warm at an alarming rate. This warming is causing a number of problems, such as rising sea levels, more extreme weather events, and changes in plant and animal life.
To reduce the impact of climate change, we need to reduce our emissions of greenhouse gases. We can do this by using less energy, using renewable energy sources, and improving energy efficiency. We also need to protect our forests, which absorb carbon dioxide from the atmosphere.
Option B is incorrect because the average surface temperature would be much lower without the greenhouse effect. Option C is incorrect because the average surface temperature would be different without the greenhouse effect. Option D is incorrect because the average surface temperature would be more variable without the greenhouse effect.