Explanation:

- The Asian Infrastructure Investment Bank (AIIB) is a multilateral development bank focused on infrastructure investment in Asia.

- Option 1: Tokyo

- Tokyo is the capital of Japan, but it is not the headquarters of AIIB.

- Option 2: Beijing

- Beijing is the capital of China and is indeed where the AIIB's headquarters is located.

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- Option 3: Singapore

- Singapore is a major financial hub in Asia but it is not the location of the AIIB's headquarters.

- Option 4: Malaysia

- Malaysia is a Southeast Asian country, but it is not where the AIIB is headquartered.

- Option 5: Philippines

- The Philippines is another Southeast Asian nation but not the host of the AIIB headquarters.

Thus, the correct answer is indeed Beijing, as you indicated.