The correct options are
B Many new people joined the group as it marched to the coast.
C Gandhi broke the Salt Law by collecting natural salt.
D This was a form of tax resistance and non-violent protest.
The Dandi March began on 12 March, 1930, and ended on 6 April, 1930. The group started from Sabarmati Ashram in Ahmedabad, and walked all the way to Dandi, which is on the coast of the Arabian Sea. People joined them in huge numbers. On reaching the shore, Gandhi and his followers broke the Salt Law by collecting natural salt. This was a form of non-violent protest against unjust colonial policies of taxation.