Singer-actor Justin Timberlake has been challenged to a dance off by corporal Kelsey De Santis, his date for the US Marine Corps Ball. Timberlake is taking Santis to ball and she has warned him he’d better have his dance moves in order, reported TMZ online. “My friends keep saying, ‘Dance-off!’ They know about my skills. I honestly don’t think he’ll be able to keep up with my group of people. I don’t think he’ll be able to keep up with us,” Santis joked.