A police report from the Central Provinces in 1930 recorded that most…

The correct answer is Option (4) → The inauguration of Gandhiji's march to the sea

Option (1) The arrest of Jawaharlal Nehru on his way to a meeting — Incorrect. Nehru's arrest at Cheoki station came later, in April, and the report from the United Provinces records it. The empty schools in Nagpur were not linked to it.

Option (2) The Lahore Congress call for complete independence — Incorrect. The Lahore Congress resolved on Purna Swaraj and set 26 January as Independence Day. That came weeks before the salt march began.

Option (3) The opening of the Round Table Conference in London — Incorrect. The Round Table Conferences in London began only later in 1930. Nothing in the Nagpur report connects the empty schools to them.

Option (4) The inauguration of Gandhiji's march to the sea — Correct. The Central Provinces report records that the schools and colleges of Nagpur were deserted to mark the inauguration of Gandhi's march. Students stayed away to show support for the start of the salt march.