Answer:
Lower pressure causes the papers to move closer to each other.
Explanation:
As we know by Bernoulli's principle

so here when air between the two papers is at normal situation then let say the pressure between the two papers is 
now if the air between two papers is blown by straw then the speed of air between two papers will increase.
So as per the equation above the pressure will decrease as the sum of pressure and kinetic energy per unit volume must be constant.
So here the pressure between two papers will decrease due to which the two papers will come closer to each other.
so correct answer will be
Lower pressure causes the papers to move closer to each other.