What did Gandhi do to break the salt law?

A civil-disobedience movement is a deliberate, non-violent act that publicly defies one specific unjust law. To identify which campaign broke a particular law, look for the action that was aimed directly at that law itself, rather than at a different economic or social grievance.

The British colonial government held a monopoly on salt production and taxed it, making it illegal for Indians to make or sell salt on their own. To directly defy this salt law, Gandhi led the Dandi March (also called the Salt March) from 12 March to 6 April 1930 -- a roughly 240-mile walk from Sabarmati Ashram to the coastal village of Dandi, where he manufactured salt from seawater in open violation of the law, launching the wider Salt Satyagraha across the country.

• Ahmedabad March: this refers to the 1918 Ahmedabad mill strike, where Gandhi mediated a wage dispute between textile mill owners and workers using a hunger strike -- a labour-wage grievance, unconnected to any tax on salt.

• Champaran March: this refers to the 1917 Champaran Satyagraha in Bihar, where Gandhi supported indigo cultivators against the forced tinkathia cultivation system imposed by British planters -- a land-tenancy grievance, also unconnected to salt.

• All: since the Ahmedabad and Champaran campaigns addressed a wage dispute and a tenancy dispute respectively, and neither targeted the salt law, grouping all three together does not hold.

Of the movements listed, only the Dandi March was organised specifically to break the salt law.