The correct options are
A The negotiations and satyagraha movements failed.
B The portugese did not want to let go of their symbol of prestige.
D The military operation was a retaliation to the deaths of unarmed activists by the Portuguese on 15 August 1955.
Goa was a symbol of prestige for the Portuguese and all negotiations failed. On 15 August 1955, several unarmed activists attempted to enter Goa where they were stopped by the Portuguese resulting in several deaths. After this, India took a radical step and launched a military operation.