Task: Question Answering
Input (English): Background Paragraph: A large log placed in a fire will burn relatively slowly. If the same mass of wood were added to the fire in the form of small twigs, they would burn much more quickly. This is because the twigs provide a greater surface area than the log does. An increase in the surface area of a reactant increases the rate of a reaction. Surface area is larger when a given amount of a solid is present as smaller particles. A powdered reactant has a greater surface area than the same reactant as a solid chunk. In order to increase the surface area of a substance, it may be ground into smaller particles or dissolved into a liquid. In solution, the dissolved particles are separated from each other and will react more quickly with other reactants. 
Story: Two groups of teens studied fire for the physics class. Group S made a fire using large logs, while group F made a fire using small twigs and sawdust. Both groups used the same volume of wood. 
Question: Which group provided a smaller surface area for an increased rate of the burning reaction?
Output (English): Group S.