Final answer:
If the albedo of the Earth were to be 21, the global temperature would increase.
Step-by-step explanation:
The albedo of the Earth refers to the amount of solar radiation reflected from the Earth's surface. If the albedo of the Earth were to be 21, it would mean that 21% of the sunlight that reaches the planet is reflected. A lower albedo value would indicate that more sunlight is being absorbed by the Earth's surface. Since the Earth would be absorbing more sunlight, this would result in an increase in global temperature. Therefore, the correct answer is 1) The global temperature would increase.