OMAHA, Neb.--(BUSINESS WIRE)--TD Ameritrade, Inc.1 invites college students nationwide to compete in the second-annual thinkorswim® Challenge. Students can register to participate in the simulated trading competition, which is designed to help teach the next generation of investors about engaging with the market. Prizes will be awarded to participants and their schools based on the performance of their virtual trading portfolios over a four-week time frame beginning October 12, 2015. “The next