Assertion: Nehru was against nuclear weapons.
Reason: Nehru believed it was not possible for a developing country like India to develop a nuclear arsenal.

The Assertion is correct but the Reason is incorrect.

Nehru had always put his faith in science and technology for rapidly building a modern India. A significant component of his industrialization plans was the nuclear program initiated in the late 1940s under the guidance of Homi J. Bhabha. India wanted to generate atomic energy for peaceful purposes. Nehru was against nuclear weapons. So he pleaded with the superpowers for comprehensive nuclear disarmament. However, the nuclear arsenal kept rising.