Task: Question Generation
Input (English): Background Paragraph: Many reactions take place in solution or in the gas phase, where the reactants are evenly dispersed throughout a homogeneous mixture. However, for reactions in which one of the reactants is a pure solid or liquid (meaning that this reactant is not already mixed together with any other reactants), reactivity only occurs at the surface, where particles of the solid or liquid reactant come into contact with particles of the other reactants. All of the molecules or ions in the interior of the pure substance will not be colliding with the other necessary reactants, so they are not really contributing to the overall rate of the reaction. However, increasing the surface area will increase the frequency of potentially reactive collisions, because more reactant particles will be in contact with the other necessary reactants. 
Story: Mike was preparing for his chemistry exam. To see the chemistry concepts in practice he conducted two tests, test A and test B. In test A he used two liquid reactants evenly dispersed, but in test B he used one liquid reactant and one solid reactant. He was surprised to see that two tests had very different results.
Output (English): In which test less reactant particles would be in contact with other reactants, test A or test B?