The correct answer is (a). The Naxalite movement, which originated in West Bengal, had a presence in parts of Andhra Pradesh, primarily in the tribal areas of the Eastern Ghats. The Naxalites are a communist revolutionary movement that has been active in India since the late 1960s. They are known for their use of violence and their attacks on government and security forces. The Naxalite movement is strongest in the tribal areas of the Eastern Ghats, where they have a significant following among the tribal people. The Naxalites have been able to gain a foothold in these areas due to the poverty and lack of development in these regions. The Naxalite movement is a major security threat to India, and the government has been struggling to contain it for decades.
The other options are incorrect. Option (b) is incorrect because the Naxalites are not active in urban industrial centers. Option (c) is incorrect because the Naxalites are not active in coastal districts. Option (d) is incorrect because the Naxalites are not active in fertile agricultural regions.