Given the task definition and input, reply with output. This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.

Passage: From January 1820, 2010 a national conference on Tibet and areas inhabited by Tibetans in Sichuan, Yunnan, Gansu and Qinghai was held in China and a substantial plan to improve development of the areas was announced. The conference was attended by General secretary Hu Jintao, Wu Bangguo, Wen Jiabao, Jia Qinglin, Li Changchun, Xi Jinping, Li Keqiang, He Guoqiang and Zhou Yongkang, all members of CPC Politburo Standing Committee signaling the commitment of senior Chinese leaders to development of Tibet and ethnic Tibetan areas. The plan calls for improvement of rural Tibetan income to national standards by 2020 and free education for all rural Tibetan children. China has invested 310 billion yuan (about 45.6 billion U.S. dollars) in Tibet since 2001. "Tibet's GDP was expected to reach 43.7 billion yuan in 2009, up 170 percent from that in 2000 and posting an annual growth of 12.3 percent over the past nine years."
Who attended the 2018 conference on Tibet?