Hey there! Here is the answer:
B.) decrease; increase
Here's why:
As you move from left to right across a period on the periodic table the size of an atom will decrease. As you move from top to bottom down a group on the periodic table the size of an atom will increase.
I really hope this answer helps you out! :)
Answer:

Explanation:
We have two pressures, two temperatures, and one volume.
This looks like a question in which we can use the Combined Gas Law to calculate the volume.

Data:

Calculation:

I think it's B. Molecules collide more frequently
Another name for chemical change would be chemical reaction.