The correct answer is: A. Environmentalist and Social Activist.
Chandi Prasad Bhatt is a well-known Indian environmentalist and social activist. He is the founder of the Chipko Movement, a non-violent protest against deforestation in the Himalayas. He is also the founder of the Dasholi Gram Swaraj Mandal, a non-profit organization that works to promote sustainable development in the Himalayas.
B. Economist and Writer is incorrect because Chandi Prasad Bhatt is not an economist or a writer.
C. Painter is incorrect because Chandi Prasad Bhatt is not a painter.
D. Classical Hindustani Vocalist is incorrect because Chandi Prasad Bhatt is not a classical Hindustani vocalist.