(a) Jawaharlal Nehru's first visit to the Soviet Union
(b) Nikita Khrushchev's first visit to India
(c) Morarji Desai's visit to the Soviet Union as Indian Prime Minister
(d) Signing of Indo-Soviet Treaty of Peace, Friendship and Cooperation
Codes:
Correct Answer: A. (a), (b), (d), (c)