Decreases, stays the same, increases.
The volume decreases because as air is cooled, the individual molecules collectively possess less kinetic energy and the distances between them decrease, thus leading to a decrease in the volume they occupy at a certain pressure (please note that my answer only holds under constant pressure; air, as a gas, doesn't actually have a definite volume).
The mass stays the same because physical processes do not create or destroy matter. The law of conservation of mass is obeyed. You're only cooling the air, not adding more air molecules.
The density decreases because as the volume decreases and mass stays the same, you have the same mass occupying a smaller volume. Density is mass divided by volume, so as mass is held constant and volume decreases, density increases.
Answer: it is D. it is the only possible answer. use the process of elimination. which answers make sense?
To what i see, the answer is....
C.
A shorter electromagnetic wave is hotter.
A shorter electromagnetic wave produce heat hotter than ultraviolet rays. Because it produces both gamma rays and ultraviolet rays that makes it hotter that the heat of the sun.
An object with high mass accelerating quickly. Assuming the objects have the same volume, the third choice will be the most dense, and therefore will take a longer time and a stronger opposite force to slow it down to a complete stop due to its high acceleration rate, as well.
Pretty good for a 13 year old, huh? :D