The quadruplet sisters Zhu Wanbing, Zhu Wanqing, Zhu Wanyu and Zhu Wanjie (from L to R) celebrate their 10th birthday at a restaurant in Nanjing, east China's Jiangsu Province, Aug. 11, 2009. The quardruplet sisters were naturally conceived and born on August 11, 1999 in Nanjing. [Xinhua]