A dialogue between Rajiv Gandhi and AASU was held in 1980's, which led to the signing of an accord in 1985. AASU stands for:

All Assam Students Union

The correct answer is Option 3 - All Assam Students Union

In 1979 the All Assam Students’ Union (AASU), a students’ group not affiliated to any party, led an anti-foreigner movement. The movement was against illegal migrations, against domination of Bengalis and other outsiders, and against faulty voters’ register that included the names of lakhs of immigrants. The movement demanded that all outsiders who had entered the State after 1951 should be sent back. The agitation followed many novel methods and mobilised all sections of Assamese people, drawing support across the State. It also involved many tragic and violent incidents leading to loss of property and human lives. The movement also tried to blockade the movement of trains and the supply of oil from Assam to refineries in Bihar.