The correct answer is: C. 30 percent.
Albedo is the fraction of incident light that is reflected by a surface. The Earth’s albedo is the average albedo of the Earth’s surface, including the land, oceans, and atmosphere. The Earth’s albedo is about 30%, which means that about 30% of the sunlight that hits the Earth is reflected back into space. The Earth’s albedo is affected by a number of factors, including the amount of cloud cover, the type of surface, and the angle of the sun.
Option A: 4 percent is too low. The Earth’s albedo is about 30%, so 4% is too low.
Option B: 10 percent is too low. The Earth’s albedo is about 30%, so 10% is too low.
Option C: 30 percent is the correct answer. The Earth’s albedo is about 30%.
Option D: 50 percent is too high. The Earth’s albedo is about 30%, so 50% is too high.
Option E: 90 percent is too high. The Earth’s albedo is about 30%, so 90% is too high.