When Ayub Khan paid a state visit to China:

President Ayub Khan of Pakistan paid a significant state visit to China in 1965. Specifically, this landmark visit occurred in March 1965. This trip was instrumental in solidifying the strategic alliance between Pakistan and China, fostering closer economic, political, and military cooperation, especially in the context of regional geopolitical dynamics and the impending 1965 Indo-Pakistani War. Options A (1961), B (1963), and D (1968) are incorrect dates for this pivotal state visit that strengthened bilateral ties.