In which year did the All Assam Students’ Union (AASU) lead an anti-foreigner movement?

The correct option is 1979.

Explanation:
The All Assam Students’ Union (AASU) spearheaded a major popular movement in Assam, known as the Assam Movement or the Assam Agitation. This movement was launched to identify and deport illegal immigrants, whom the protestors termed "foreigners" (primarily from Bangladesh), who had settled in Assam.
The anti-foreigner agitation officially began in 1979 and continued for six years, concluding with the signing of the Assam Accord on August 15, 1985, between the leaders of the movement and the Government of India.