The mean temperature of Earth is the average temperature across the entire planet. Option 1, which states 6 degrees Celsius, is not correct because it is too low and does not accurately represent the global average temperature. Option 2, which states 16 degrees Celsius, is the correct answer because it is the closest to the actual average temperature of Earth. Option 3, which states 26 degrees Celsius, is too high and is not an accurate reflection of the global average temperature. Option 4, which states 36 degrees Celsius, is also too high and does not represent the true mean temperature of Earth. Therefore, option 2 is the correct answer.