I agree with 1 and 2. I don't agree with 3 and 4. For 5 I agree with your answer; however, I think B is correct also.
I don't understand how you can answer 3 or 4 incorrectly. Let me pick one of those and go through it with you. Here is 4
"4. When the pressure of a gas decreases, which quantity will increase, assuming all other variables are held constant?(1 point)"
So PV = nRT. Do these one at a time. I'll start with T.
option 1. If V, n R are constant we can rewrite the equation as P*k = k*T so if P goes sown T must go down.
option 2. R. But you know R is a constant and won't change.
option 3. n. PV = nRT. P*k = n*k. Same as #1. If P goes down n must go down.
option 4. V. PV = nRT. PV = k. So if P goes down, V MUST go up to keep k constant. For example. if you consider P = 2 and V = 4 then k = 8. So we halve P to 1 we must double V to 8 so that 1*8 = 8. So the answer is that by decreasing P the only variable going up is V.