Q: 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: After the Xinhai Revolution (191112) toppled the Qing dynasty and the last Qing troops were escorted out of Tibet, the new Republic of China apologized for the actions of the Qing and offered to restore the Dalai Lama's title. The Dalai Lama refused any Chinese title and declared himself ruler of an independent Tibet. In 1913, Tibet and Mongolia concluded a treaty of mutual recognition. For the next 36 years, the 13th Dalai Lama and the regents who succeeded him governed Tibet. During this time, Tibet fought Chinese warlords for control of the ethnically Tibetan areas in Xikang and Qinghai (parts of Kham and Amdo) along the upper reaches of the Yangtze River. In 1914 the Tibetan government signed the Simla Accord with Britain, ceding the South Tibet region to British India. The Chinese government denounced the agreement as illegal.
A:
What revolution took place in 1913?