Aballoon will get smaller when it's filled with air, when air is heated, or cooled, or when it rises?

Assuming the balloon is untied aka the air inside isn't intact.

It will get smaller when it rises.

As it air is cooled, a balloon will get smaller. 

to better understand this, we should recall the properties of gases

when we have pressure, volume and temperature, they are all proportional to each except pressure and volume. 

so, if air is heated, meaning temperature is increased, that means volume increases. (get's bigger-- not the answer)

if balloon rises, as it goes up, the pressure decreases, if pressure decreases, volume increases

when the air is cooled, meaning temperature is decreased, that means volume decreases as well. 

29.1-12=17.1the answer is this one