The correct answer is: C. Increase, decrease.
The saturation vapor pressure of air is the pressure exerted by water vapor in the air when it is in equilibrium with a liquid or solid surface of water. The saturation vapor pressure of air increases with increasing temperature. This is because the molecules of water vapor have more energy at higher temperatures and can therefore move faster and collide with the surface of the water more often.
The relative humidity of air is the ratio of the actual vapor pressure of the air to the saturation vapor pressure of the air at the same temperature. The relative humidity of air decreases with increasing temperature. This is because the saturation vapor pressure of air increases with increasing temperature, so the actual vapor pressure of the air becomes a smaller fraction of the saturation vapor pressure at higher temperatures.
If very cold air is brought indoors and warmed with no change in its moisture content, the saturation vapor pressure of this air will increase. This is because the temperature of the air is increasing, and the saturation vapor pressure of air increases with increasing temperature. The relative humidity of this air will decrease. This is because the actual vapor pressure of the air is not changing, but the saturation vapor pressure of the air is increasing. Therefore, the actual vapor pressure of the air becomes a smaller fraction of the saturation vapor pressure at higher temperatures.