Task: Question Answering
Input (English): Background Paragraph: Almost all earthquakes occur at plate boundaries. All types of plate boundaries have earthquakes. Convection within the Earth causes the plates to move. As the plates move, stresses build. When the stresses build too much, the rocks break. The break releases the energy that was stored in the rocks. The sudden release of energy creates an earthquake. During an earthquake the rocks usually move several centimeters or rarely as much as a few meters. Elastic rebound theory describes how earthquakes occur ( Figure below ). 
Story: Two brothers loved geology. Bob studied sedimentary rocks while Dan studied about earthquakes and their location. 
Question: Which brother studied less about how rocks usually move several centimeters?
Output (English): Bob.