Definition: In this task, you're given a question, along with a context passage which has extra information available on certain terms mentioned in it. Your job is to determine which sentence(s) from the passage can be used to search for further information needed to answer the question.
Input: Question: How long had Britain had control of Hong Kong before returning it to China? Passage:As a result of negotiations and the 1984 agreement between China and Britain, Hong Kong was returned to China and became its first Special Administrative Region on 1 July 1997, under the principle of "one country, two systems". Hong Kong has a different political system from mainland China. Hong Kong's independent judiciary functions under the common law framework. The Hong Kong Basic Law, the constitutional document drafted by the Chinese side before the handover based on the terms enshrined in the Joint Declaration, governs its political system, and stipulates that Hong Kong shall have a high degree of autonomy in all matters except foreign relations and military defence. The declaration stipulates that the region maintain its capitalist economic system and guarantees the rights and freedoms of its people for at least 50 years after the 1997 handover. The guarantees over the territory's autonomy and the individual rights and freedoms are enshrined in the Hong Kong Basic Law, which outlines the system of governance of the Hong Kong Special Administrative Region, but which is subject to the interpretation of the Standing Committee of the National People's Congress (NPCSC).

Output:
As a result of negotiations and the 1984 agreement between China and Britain, Hong Kong was returned to China and became its first Special Administrative Region on 1 July 1997, under the principle of "one country, two systems"