What was the reason behind Lal Bahadur Shastri's resigning from the position of Railway Minister?

Moral responsibility for a major railway accident

The correct answer is Option (3) → Moral responsibility for a major railway accident

" The ease with which the succession after Nehru took place proved all the critics wrong. When Nehru passed away, K. Kamraj, the president of the Congress party consulted party leaders and Congress members of Parliament and found that there was a consensus in favour of Lal Bahadur Shastri. He was unanimously chosen as the leader of the Congress parliamentary party and thus became the country’s next Prime Minister. Shastri was a non-controversial leader from Uttar Pradesh who had been a Minister in Nehru’s cabinet for many years. Nehru had come to depend a lot on him in his last year. He was known for his simplicity and his commitment to principles. Earlier he had resigned from the position of Railway Minister accepting moral responsibility for a major railway accident."