宇宙大爆炸理论揭示了宇宙的起源。国产学生

　　At the height of the Roaring Twenties, music scouts armed with cutting-edge recording technology set out across America to capture the unknown voices of everyday folk. The recordings they made captured the country's diversity - artistically, ethnically, geographically, and economically. As told by music pioneers, their families and eyewitnesses to the era, we travel back in tim... (展开全部)