1. Ideal gas particles:

Question

A. have no mutual attraction and no individual volume.
B. have no mass or volume.
C. have no odor and no color.
D. have no density and do not form bonds.
Is it A?

2. Why does the density of gas in a hot air balloon decrease as the gas is heated?

A. The volume of gas decreases as temperature increases.
B. The mass of gas increases as temperature increases.
C. The mass of gas decreases as temperature increases.
D. The volume of gas increases as temperature increases.

Is it D?

3. During which stroke of a four-stroke internal combustion engine is the system's temperature raised because work is done to the gases?

A. Intake stroke
B. Power stroke
C. Compression stroke
D. Exhaust stroke

I have no idea

Answer 1

1 and 2 are right.
I'm not an internal combustion man but I think the answer is c. The compression stroke is when the piston is at the bottom of it's stroke and it has just pulled in the fuel, then it starts up and compresses the gas so that the gas occupies the smallest volume just before the firing takes place (the firing starts the power stroke) and work is done on the gas as it is compressed.