You are given a question or fill-in-the-blank question, two answer options (Option1 and Option2) and an Explanation. Your task is to find the correct answer (return the string of the correct option, not option1/2) for the given question from the given options and using explanation.

[EX Q]: Question: A piece of sandpaper was rubbed across a glass table, then the sandpaper was rubbed across some gravel. The friction will be greater between 
 Option1: the sandpaper and the glass table or 
 Option2: the sandpaper and the gravel. 
 Explanation: Rougher surfaces have more friction between them than smoother surfaces.
[EX A]: the sandpaper and the gravel.

[EX Q]: Question: Would Jim's solution become more or less acidic if he decreased the concentration of hydrogen atoms in it? 
 Option1: more acidic 
 Option2: less acidic 
 Explanation: With a higher the concentration of hydrogen ions, a solution is more acidic and has a lower pH.
[EX A]: less acidic

[EX Q]: Question: Mike is watching how particles of reactants function, and sees that they are very far apart. Considering that the concentration of them is very low, the chance of them colliding together is 
 Option1: high 
 Option2: low 
 Explanation: At higher concentrations, particles of reactants are crowded closer together, so they are more likely to collide and react.
[EX A]:
low