Please answer the following question: Information:  - The Beiyang Army (Pei-yang Army) was a powerful, Western-style Imperial Chinese Army established by the Qing Dynasty government in the late 19th century. It was the centerpiece of a general reconstruction of Qing China's military system. The Beiyang Army played a major role in Chinese politics for at least three decades and arguably right up to 1949. It made the Xinhai Revolution of 1911 possible, and, by dividing into warlord factions known as the Beiyang Clique (Pei-yang Clique), ushered in a period of regional division.  - Yuan Shikai (16 September 1859  6 June 1916) was a Chinese general, politician and warlord, famous for his influence during the late Qing Dynasty, his role in the events leading up to the abdication of the last Qing Emperor, his autocratic rule as the first formal President of the Republic of China, and his short-lived attempt to restore monarchy in China, with himself as the Hongxian Emperor.  - A warlord is a leader able to exercise military, economic, and political control over a subnational territory within a sovereign state due to his ability to mobilize loyal armed forces. These armed forces, usually considered militias, are loyal to the warlord rather than to the state regime. Warlords have existed throughout much of history, albeit in a variety of different capacities within the political, economic, and social structure of states or ungoverned territories.  - Korea is a historical state in East Asia, since 1945 divided into two distinct sovereign states: North Korea (officially the "Democratic People's Republic of Korea") and South Korea (officially the "Republic of Korea"). Located on the Korean Peninsula, Korea is bordered by China to the northwest and Russia to the northeast. It is separated from Japan to the east by the Korea Strait and the East Sea.  - A courtesy name ("zi"), also known as a style name, is a name bestowed upon one at adulthood in addition to one's given name. This practice is a tradition in East Asian cultures, including China, Japan, Korea, and Vietnam.  - Japan ("Nippon" or "Nihon" ; formally "" or "Nihon-koku", means "State of Japan") is a sovereign island nation in Eastern Asia. Located in the Pacific Ocean, It is lying off the eastern coast of the Asia Mainland (east of China, Korea, Russia) and stretching from the Sea of Okhotsk in the north to the East China Sea and near Taiwan in the southwest.   - The Zhili clique was one of several mutually hostile cliques or factions that split from the Beiyang clique during the Republic of China's warlord era. This fragmentation followed the death of Yuan Shikai, who was the only person capable of keeping the Beiyang Army together. It was named for the general region of the clique's base of power, Zhili Province, now Hebei.   - China, officially the People's Republic of China (PRC), is a unitary sovereign state in East Asia. With a population of over 1.381 billion, it is the world's most populous country. The state is governed by the Communist Party of China, and its capital is Beijing. It exercises jurisdiction over 22 provinces, five autonomous regions, four direct-controlled municipalities (Beijing, Tianjin, Shanghai, and Chongqing), and two mostly self-governing special administrative regions (Hong Kong and Macau), and claims sovereignty over Taiwan. The country's major urban areas include Shanghai, Guangzhou, Beijing, Chongqing, Shenzhen, Tianjin and Hong Kong. China is a great power and a major regional power within Asia, and has been characterized as a potential superpower.  - Cao Kun ( Courtesy name : Zhongshan (  ) ) ( December 12 , 1862 -- May 15 , 1938 ) was a President of Republic China and military leader of the Zhili clique in the Beiyang Army , he also served as trustee of the Catholic University of Peking .    After reading the paragraphs above, we are interested in knowing the entity with which 'cao kun' exhibits the relationship of 'position held'. Find the answer from the choices below.  Choices: - leader  - politician  - president  - president of the republic of china  - sovereign
A:
president of the republic of china