<P> The title of emperor was hereditary, traditionally passed on from father to son in each dynasty . There are also instances where the throne is assumed by a younger brother, should the deceased Emperor have no male offspring . By convention in most dynasties, the eldest son born to the Empress (嫡 長子 / 嫡 长子) succeeded to the throne . In some cases when the empress did not bear any children, the emperor would have a child with another of his many wives (all children of the emperor were said also to be the children of the empress, regardless of birth mother). In some dynasties the succession of the empress' eldest son was disputed, and because many emperors had large numbers of progeny, there were wars of succession between rival sons . In an attempt to resolve after - death disputes, the emperor, while still living, often designated a Crown Prince (太子). Even such a clear designation, however, was often thwarted by jealousy and distrust, whether it was the crown prince plotting against the emperor, or brothers plotting against each other . Some emperors, like the Yongzheng Emperor, after abolishing the position of Crown Prince, placed the succession papers in a sealed box, only to be opened and announced after his death . </P> <P> Unlike, for example, the Japanese monarchy, Chinese political theory allowed for a change in the ruling house . This was based on the concept of the "Mandate of Heaven". The theory behind this was that the Chinese emperor acted as the "Son of Heaven" and held a mandate to rule over everyone else in the world; but only as long as he served the people well . If the quality of rule became questionable because of repeated natural disasters such as flood or famine, or for other reasons, then rebellion was justified . This important concept legitimized the dynastic cycle or the change of dynasties . </P> <P> This principle made it possible even for peasants to found new dynasties, as happened with the Han and Ming dynasties, and for the establishment of conquest dynasties such as the Mongol - led Yuan dynasty and Manchu - led Qing dynasty . It was moral integrity and benevolent leadership that determined the holder of the "Mandate of Heaven". </P> <P> There has been only one lawful female reigning Emperor in China, Empress Zetian of the Tang dynasty or the Zhou (Wu - Chou) dynasty founded by her . Many women, however, did become de facto leaders, usually as Empress Dowager . Prominent examples include Empress Dowager Cixi, mother of the Tongzhi Emperor (1861--1874), and aunt and adoptive mother of the Guangxu Emperor (1874--1908), who ruled China for 47 years (1861--1908), and the Empress Dowager Lü of the Han dynasty . </P>

Which one of the following was elevated to the status of queen of heaven by the emperor of china