The correct answer is: A. Enhance the atmospheric greenhouse effect.
Low clouds reflect sunlight back to space during the day, which helps to cool the Earth’s surface. However, at night, low clouds trap heat near the surface, which helps to warm the Earth. This is because low clouds are made up of water droplets, which are good at absorbing and emitting infrared radiation. When the sun is not shining, the Earth’s surface emits infrared radiation, which is absorbed by the water droplets in the clouds. This energy is then re-radiated back to the Earth’s surface, which helps to warm it.
Option B is incorrect because low clouds actually help to warm the Earth at night. Option C is incorrect because low clouds are not caused by the atmospheric greenhouse effect. Option D is incorrect because low clouds do have an effect on the atmospheric greenhouse effect.