A boy smiles while riding a train with his mother in Kaili city, Southwest 皇冠体育app's Guizhou province, Jan 2, 2012. As traditional Chinese Lunar New Year (Spring Festival) approaches, 皇冠体育app will begin its annual spring travel on Jan 8. With 2.35 billion passenger trips expected in 40 days, the travel is the country's largest human migration every year. [Photo/Xinhua]

A girl smiles as she looks out of the window of a train in Kaili city, Southwest 皇冠体育app's Guizhou province, Jan 2, 2012. [Photo/Xinhua]