Which one of the following became a part of China in 1997 following the principle of ‘one country, two systems’?

Hong Kong became a Special Administrative Region (SAR) of China on July 1, 1997, following the end of British colonial rule [2]. The transition was governed by the 1984 Sino-British Joint Declaration, which established the 'one country, two systems' principle. This framework guaranteed Hong Kong a high degree of autonomy, preserving its capitalist system and legal framework for fifty years after the handover [4]. In contrast, Tibet was incorporated into the People's Republic of China much earlier, with China establishing full control by May 1951. Tibet was later designated as an autonomous region in 1965. Xinjiang and Inner Mongolia are also autonomous regions of China but were not part of the 1997 'one country, two systems' handover agreement [1]. The principle was specifically designed to facilitate the peaceful reunification of Hong Kong and later Macau with mainland China.

Sources

1. [2] https://www.cfr.org/backgrounder/hong-kong-freedoms-democracy-protests-china-crackdown
2. [4] https://us.china-embassy.gov.cn/eng/zt/bps/201504/t20150415_4911445.htm
3. [1] https://www.bbc.com/news/world-asia-china-40426827