When the air temperature increases, the saturation vapour pressure will:

The correct answer is A. Increase.

Saturation vapor pressure is the maximum amount of water vapor that can be in the air at a given temperature. It increases as the temperature increases because the molecules of water have more energy and can move faster. This means that they can escape from the surface of the water and enter the air more easily.

Option B is incorrect because the saturation vapor pressure increases as the temperature increases.

Option C is incorrect because the saturation vapor pressure does not remain the same as the temperature increases.

Option D is incorrect because the saturation vapor pressure does not vary over an increasingly broad range of values as the temperature increases.